Faq for Gasoline

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From: Bruce Hamilton

Newsgroups: rec.autos.techSubject: Gasoline FAQ - Part 1 of 4Date: Thu, 15 Jan 2004 22:15:11 +1300Message-ID: Reply-To:[email protected]

Archive-name: autos/gasoline-faq/part1Posting-Frequency: monthlyLast-modified: 17 November 1996Version: 1.12

FAQ: Automotive GasolineBruce Hamilton

[email protected]

This FAQ is posted monthly to the Usenet groups news.answers, rec.answers,and rec.autos.tech. The latest copy should be available on the WWW from sitesthat automatically convert those FAQs, such as www.faqs.org.

Changes:- added a little more data on US crude oil resources.

Subject: 1. Introduction, Intent, Acknowledgements, and Abbreviations

1.1 Introduction and Intent.

The intent of this FAQ is to provide some basic information on gasolines andother fuels for spark ignition engines used in automobiles. The toxicity andenvironmental reasons for recent and planned future changes to gasoline arediscussed, along with recent and proposed changes in composition of gasoline.This FAQ is intended to help readers choose the most appropriate fuel forvehicles, assist with the diagnosis of fuel-related problems, and tounderstand the significance of most gasoline properties listed in fuelspecifications. I make no apologies for the fairly heavy emphasis on
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chemistry; it is the only sensible way to describe the oxidation ofhydrocarbon fuels to produce energy, water, and carbon dioxide.

1.2 Acknowledgements.

Thanks go to all the posters in sci.energy and rec.autos.tech who spend

valuable time responding to questions. I would also like to acknowledgethe considerable effort of L.M.Gibbs of Chevron, who has twice spent hisvaluable time courteously detailing errors and providing referencesfor his corrections. All remaining errors and omissions are mine.

1.3 Abbreviations.

AKI = Antiknock Index of Gasoline ( (RON+MON)/2 )CI = Compression Ignition ( Diesel )Gasoline = Petrol ( Yes, complaints were received :-) )IC = Internal CombustionMON = Motor Octane RatingOctane = The Octane Rating of the GasolineRFG = Reformulated Gasoline ( as defined by US Clean Air Act )RON = Research Octane RatingSI = Spark Ignition ( Gasoline )

Subject: 2. Table of Contents

1. Introduction, Intent, Acknowledgements, and Abbreviations1.1 Introduction and Intent.1.2 Acknowledgements.1.3 Abbreviations.

2. Table of Contents3. What Advantage will I gain from reading this FAQ?4. What is Gasoline?

4.1 Where does crude oil come from?.4.2 When will we run out of crude oil?.4.3 What is the history of gasoline?4.4 What are the hydrocarbons in gasoline?4.5 What are oxygenates?4.6 Why were alkyl lead compounds added?4.7 Why not use other organometallic compounds?4.8 What do the refining processes do?4.9 What energy is released when gasoline is burned?4.10 What are the gasoline specifications?4.11 What are the effects of the specified fuel properties?4.12 Are brands different?4.13 What is a typical composition?4.14 Is gasoline toxic or carcinogenic?4.15 Is unleaded gasoline more toxic than leaded?4.16 Is reformulated gasoline more toxic than unleaded?4.17 Are all oxygenated gasolines also reformulated gasolines?

5. Why is Gasoline Composition Changing?5.1 Why pick on cars and gasoline?5.2 Why are there seasonal changes?5.3 Why were alkyl lead compounds removed?
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5.4 Why are evaporative emissions a problem?5.5 Why control tailpipe emissions?5.6 Why do exhaust catalysts influence fuel composition?5.7 Why are "cold start" emissions so important?5.8 When will the emissions be "clean enough"?5.9 Why are only some gasoline compounds restricted?

5.10 What does "renewable" fuel or oxygenate mean?5.11 Will oxygenated gasoline damage my vehicle?5.12 What does "reactivity" of emissions mean?5.13 What are "carbonyl" compounds?5.14 What are "gross polluters"?

6. What do Fuel Octane ratings really indicate?6.1 Who invented Octane Ratings?6.2 Why do we need Octane Ratings?6.3 What fuel property does the Octane Rating measure?6.4 Why are two ratings used to obtain the pump rating?6.5 What does the Motor Octane rating measure?6.6 What does the Research Octane rating measure?6.7 Why is the difference called "sensitivity"?6.8 What sort of engine is used to rate fuels?6.9 How is the Octane rating determined?6.10 What is the Octane Distribution of the fuel?6.11 What is a "delta Research Octane number"?6.12 How do other fuel properties affect octane?6.13 Can higher octane fuels give me more power?6.14 Does low octane fuel increase engine wear?6.15 Can I mix different octane fuel grades?6.16 What happens if I use the wrong octane fuel?6.17 Can I tune the engine to use another octane fuel?6.18 How can I increase the fuel octane?6.19 Are aviation gasoline octane numbers comparable?6.20 Can mothballs increase octane?

7. What parameters determine octane requirement?7.1 What is the Octane Number Requirement of a Vehicle?7.2 What is the effect of Compression ratio?7.3 What is the effect of changing the air-fuel ratio?7.4 What is the effect of changing the ignition timing7.5 What is the effect of engine management systems?7.6 What is the effect of temperature and Load?7.7 What is the effect of engine speed?7.8 What is the effect of engine deposits?7.9 What is the Road Octane Number of a Fuel?7.10 What is the effect of air temperature?.7.11 What is the effect of altitude?.7.12 What is the effect of humidity?.7.13 What does water injection achieve?.

8. How can I identify and cure other fuel-related problems?8.1 What causes an empty fuel tank?8.2 Is knock the only abnormal combustion problem?8.3 Can I prevent carburetter icing?8.4 Should I store fuel to avoid the oxygenate season?8.5 Can I improve fuel economy by using quality gasolines?8.6 What is "stale" fuel, and should I use it?8.7 How can I remove water in the fuel tank?8.8 Can I use unleaded on older vehicles?


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8.9 How serious is valve seat recession on older vehicles?9. Alternative Fuels and Additives

9.1 Do fuel additives work?9.2 Can a quality fuel help a sick engine?9.3 What are the advantages of alcohols and ethers?9.4 Why are CNG and LPG considered "cleaner" fuels.

9.5 Why are hydrogen-powered cars not available?9.6 What are "fuel cells" ?9.7 What is a "hybrid" vehicle?9.8 What about other alternative fuels?9.9 What about alternative oxidants?

10. Historical Legends10.1 The myth of Triptane10.2 From Honda Civic to Formula 1 winner.

11. References11.1 Books and Research Papers11.2 Suggested Further Reading

Subject: 3. What Advantage will I gain from reading this FAQ?

This FAQ is intended to provide a fairly technical description of whatgasoline contains, how it is specified, and how the properties affect theperformance of your vehicle. The regulations governing gasoline havechanged, and are continuing to change. These changes have made much of thetraditional lore about gasoline obsolete. Motorists may wish to understanda little more about gasoline to ensure they obtain the best value, and themost appropriate fuel for their vehicle. There is no point in prematurelydestroying your second most expensive purchase by using unsuitable fuel,just as there is no point in wasting hard-earned money on higher octanefuel that your automobile can not utilize. Note that this FAQ does notdiscuss the relative advantages of specific brands of gasolines, it isonly intended to discuss the generic properties of gasolines.

Subject: 4. What is Gasoline?

4.1 Where does crude oil come from?.

The generally-accepted origin of crude oil is from plant life up to 3billion years ago, but predominantly from 100 to 600 million years ago [1]."Dead vegetarian dino dinner" is more correct than "dead dinos".The molecular structure of the hydrocarbons and other compounds presentin fossil fuels can be linked to the leaf waxes and other plant molecules ofmarine and terrestrial plants believed to exist during that era. There arevarious biogenic marker chemicals ( such as isoprenoids from terpenes,porphyrins and aromatics from natural pigments, pristane and phytane fromthe hydrolysis of chlorophyll, and normal alkanes from waxes ), whose sizeand shape can not be explained by known geological processes [2]. Thepresence of optical activity and the carbon isotopic ratios also indicate abiological origin [3]. There is another hypothesis that suggests crude oilis derived from methane from the earth's interior. The current mainproponent of this abiotic theory is Thomas Gold, however abiotic and


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extraterrestrial origins for fossil fuels were also considered at the turnof the century, and were discarded then. A large amount of additionalevidence for the biological origin of crude oil has accumulated since then.

4.2 When will we run out of crude oil?

It has been estimated that the planet contains over 6.4 x 10^15 tonnes oforganic carbon that is cycled through two major cycles, but only about 18%of that contributes to petroleum production. The primary cycle ( turnover of2.7-3.0 x 10^12 tonnes of organic carbon ) has a half-life of days todecades, whereas the large secondary cycle ( turnover 6.4 x 10^15 tonnes oforganic carbon ) has a half-life of several million years [4]. Much of thisorganic carbon is too dilute or inaccessible for current technology torecover, however the estimates represent centuries to millenia of fossilfuels, even with continued consumption at current or increased rates [5].

The concern about "running out of oil" arises from misunderstanding thesignificance of a petroleum industry measure called the Reserves/Productionratio (R/P). This monitors the production and exploration interactions.The R/P is based on the concept of "proved" reserves of fossil fuels.Proved reserves are those quantities of fossil fuels that geological andengineering information indicate with reasonable certainty can be recoveredin the future from known reservoirs under existing economic and operatingconditions. The Reserves/Production ratio is the proved reserves quantitydivided by the production in the last year, and the result will be thelength of time that those remaining proved reserves would last if productionwere to continue at the current level [6]. It is important to note theeconomic and technology component of the definitions, as the price of oilincreases ( or new technology becomes available ), marginal fields become"proved reserves". We are unlikely to "run out" of oil, as more fieldsbecome economic. Note that investment in exploration is also linked to theR/P ratio, and the world crude oil R/P ratio typically moves between20-40 years, however specific national incentives to discover oil canextend that range upward.

Concerned people often refer to the " Hubbert curves" that predict fossilfuel discovery rates would peak and decline rapidly. M. King Hubbertcalculated in 1982 that the ultimate resource base of the lower 48 states ofthe USA was 163+-2 billion barrels of oil, and the ultimate production ofnatural gas to be 24.6+-0.8 trillion cubic metres, with some additionalqualifiers. As production and proved resources were 147 billion barrels ofoil and 22.5 trillion cubic metres of gas, Hubbert was implying that volumesyet to be developed could only be 16-49 billion barrels of oil and 2.1-4.5trillion cubic metres. Technology has confounded those predictions fornatural gas [6a].

The US Geological Survey has also just increased their assessment of US( not just the lower 48 states ), inferred reserves crude oil by 60 billionbarrels, and doubled the size of gas reserves to 9.1 trillion cubic metres.When combined with the estimate of undiscovered oil and gas, the totalsreach 110 billion barrels of oil and 30 trillion cubic metres of gas [7].When the 1995 USGS estimates of undiscovered and inferred crude oil arecalculated for just the lower 48 states, they totalled ( in 1995 ) 68.9billion barrels of oil, well above Hubbert's highest estimate made in 1982.


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- tend to burn in air with a clean flame.- octane ratings depend on branching and number of carbon atoms.

alkanesnormal = continuous chain of carbons ( Cn H2n+2 )

- low octane ratings, decreasing with carbon chain length.

normal heptane C-C-C-C-C-C-C C7H16

iso = branched chain of carbons ( Cn H2n+2 )- higher octane ratings, increasing with carbon chain branching.

iso octane = C C( aka 2,2,4-trimethylpentane ) | |

C-C-C-C-C C8H18|C

cyclic = circle of carbons ( Cn H2n )( aka Naphthenes )- high octane ratings.

cyclohexane = C

/ \C C

| | C6H12C C\ /C

4.4.2 Unsaturated Hydrocarbons

- Unstable, are the remaining component of gasoline.- Tend to burn in air with a smoky flame.

Alkenes ( aka olefins, have carbon=carbon double bonds )- These are unstable, and are usually limited to a few %.

- tend to be reactive and toxic, but have desirable octane ratings.-

C| C5H10

2-methyl-2-butene C-C=C-C

Alkynes ( aka acetylenes, have carbon-carbon triple bonds )

- These are even more unstable, are only present intrace amounts, and only in some poorly-refined gasolines.

_Acetylene C=C C2H2

Arenes ( aka aromatics )- Used to be up to 40%, gradually being reduced to


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super unleaded fuels ) to replace the alkyl lead octane enhancers.

C C// \ // \C C C-C C

Benzene | || Toluene | ||

C C C C\\ / \\ /C C

C6H6 C7H8Polynuclear Aromatics ( aka PNAs or PAHs )- These are high boiling, and are only present in small amounts in gasoline.They contain benzene rings joined together. The simplest, and least toxic,is Naphthalene, which is only present in trace amounts in traditionalgasolines, and even lower levels are found in reformulated gasolines.The larger multi-ringed PNAs are highly toxic, and are not present ingasoline.

C C// \ / \\C C C

Naphthalene | || | C10H8C C C\\ / \ //

C C4.5 What are oxygenates?

Oxygenates are just preused hydrocarbons :-). They contain oxygen, which cannot provide energy, but their structure provides a reasonable antiknockvalue, thus they are good substitutes for aromatics, and they may also reducethe smog-forming tendencies of the exhaust gases [15]. Most oxygenates usedin gasolines are either alcohols ( Cx-O-H ) or ethers (Cx-O-Cy), and contain1 to 6 carbons. Alcohols have been used in gasolines since the 1930s, andMTBE was first used in commercial gasolines in Italy in 1973, and was firstused in the US by ARCO in 1979. The relative advantages of aromatics andoxygenates as environmentally-friendly and low toxicity octane-enhancers arestill being researched.

Ethanol C-C-O-H C2H5OH

C|

Methyl tertiary butyl ether C-C-O-C C4H9OCH3(aka tertiary butyl methyl ether ) |

C

They can be produced from fossil fuels eg methanol (MeOH), methyl tertiarybutyl ether (MTBE), tertiary amyl methyl ether (TAME), or from biomass, egethanol(EtOH), ethyl tertiary butyl ether (ETBE)). MTBE is produced by


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reacting methanol ( from natural gas ) with isobutylene in the liquid phaseover an acidic ion-exchange resin catalyst at 100C. The isobutylene wasinitially from refinery catalytic crackers or petrochemical olefin plants,but these days larger plants produce it from butanes. MTBE production hasincreased at the rate of 10 to 20% per year, and the spot market price inJune 1993 was around $270/tonne [15]. The "ether" starting fluids for

vehicles are usually diethyl ether (liquid) or dimethyl ether (aerosol).Note that " petroleum ethers " are volatile alkane hydrocarbon fractions,they are not a Cx-O-Cy compound.

Oxygenates are added to gasolines to reduce the reactivity of emissions,but they are only effective if the hydrocarbon fractions are carefullymodified to utilise the octane and volatility properties of the oxygenates.If the hydrocarbon fraction is not correctly modified, oxygenates canincrease the undesirable smog-forming and toxic emissions. Oxygenates do notnecessarily reduce all exhaust toxins, nor are they intended to.

Oxygenates have significantly different physical properties to hydrocarbons,and the levels that can be added to gasolines are controlled by the 1977Clean Air Act amendments in the US, with the laws prohibiting the increaseor introduction of a fuel or fuel additive that is not substantiallysimilar to any fuel or fuel additive used to certify 1975 or subsequentyears vehicles. Waivers can granted if the product does not cause orcontribute to emission device failures, and if the EPA does not specificallydecline the application after 180 days, it is taken as granted. In 1978 theEPA granted 10% by volume of ethanol a waiver, and have subsequently issuedwaivers for


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have high blending octane, and so can replace high octane aromaticsin the fuel. These aromatics are responsible for disproportionate amountsof CO and HC exhaust emissions. This is called the "aromatic substitutioneffect". Oxygenates also cause engines without sophisticated enginemanagement systems to move to the lean side of stoichiometry, thus reducingemissions of CO ( 2% oxygen can reduce CO by 16% ) and HC ( 2% oxygen can

reduce HC by 10%) [17], and other researchers have observed similarreductions also occur when oxygenates are added to reformulated gasolineson older and newer vehicles, but have also shown that NOx levels mayincrease, as also may some regulated toxins [18,19,20].

However, on vehicles with engine management systems, the fuel volume will beincreased to bring the stoichiometry back to the preferred optimum setting.Oxygen in the fuel can not contribute energy, consequently the fuel has lessenergy content. For the same efficiency and power output, more fuel has tobe burnt, and the slight improvements in combustion efficiency thatoxygenates provide on some engines usually do not completely compensate forthe oxygen.There are huge number of chemical mechanisms involved in the pre-flamereactions of gasoline combustion. Although both alkyl leads and oxygenatesare effective at suppressing knock, the chemical modes through which theyact are entirely different. MTBE works by retarding the progress of the lowtemperature or cool-flame reactions, consuming radical species, particularlyOH radicals and producing isobutene. The isobutene in turn consumesadditional OH radicals and produces unreactive, resonantly stabilisedradicals such as allyl and methyl allyl, as well as stable species such asallene, which resist further oxidation [21,22].

4.6 Why were alkyl lead compounds added?

The efficiency of a spark-ignited gasoline engine can be related to thecompression ratio up to at least compression ratio 17:1 [23]. However any"knock" caused by the fuel will rapidly mechanically destroy an engine, andGeneral Motors was having major problems trying to improve engines withoutinducing knock. The problem was to identify economic additives that couldbe added to gasoline or kerosine to prevent knock, as it was apparent thatengine development was being hindered. The kerosine for home fuels soonbecame a secondary issue, as the magnitude of the automotive knock problemincreased throughout the 1910s, and so more resources were poured into thequest for an effective "antiknock". A higher octane aviation gasoline wasrequired urgently once the US entered WWI, and almost every possiblechemical ( including melted butter ) was tested for antiknock ability [24].

Originally, iodine was the best antiknock available, but was not a practicalgasoline additive, and was used as the benchmark. In 1919 aniline was found

to have superior antiknock ability to iodine, but also was not a practicaladditive, however aniline became the benchmark antiknock, and variouscompounds were compared to it. The discovery of tetra ethyl lead, and thescavengers required to remove it from the engine were made by teams lead byThomas Midgley Jr. in 1922 [9,10,24]. They tried selenium oxychloride whichwas an excellent antiknock, however it reacted with iron and "dissolved" theengine. Midgley was able to predict that other organometallics would work,and slowly focused on organoleads. They then had to remove the lead, whichwould otherwise accumulate and coat the engine and exhaust system with lead.


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Oxygen = 15.994, Nitrogen = 14.0067, and Sulfur = 32.066.

The composition of sea level air ( 1976 data, hence low CO2 value ) isGas Fractional Molecular Weight RelativeSpecies Volume kg/mole MassN2 0.78084 28.0134 21.873983

O2 0.209476 31.9988 6.702981Ar 0.00934 39.948 0.373114CO2 0.000314 44.0098 0.013919Ne 0.00001818 20.179 0.000365He 0.00000524 4.002602 0.000021Kr 0.00000114 83.80 0.000092Xe 0.000000087 131.29 0.000011CH4 0.000002 16.04276 0.000032H2 0.0000005 2.01588 0.000001

---------Air 28.964419

For normal heptane C7H16 with a molecular weight = 100.204C7H16 + 11O2 = 7CO2 + 8H2O

thus 1.000 kg of C7H16 requires 3.513 kg of O2 = 15.179 kg of air.

The chemical stoichiometric combustion of hydrocarbons with oxygen can bewritten as:-CxHy + (x + (y/4))O2 -> xCO2 + (y/2)H2OOften, for simplicity, the remainder of air is assumed to be nitrogen,which can be added to the equation when exhaust compositions are required.As a general rule, maximum power is achieved at slightly rich, whereasmaximum fuel economy is achieved at slightly lean.

The energy content of the gasoline is measured by burning all the fuelinside a bomb calorimeter and measuring the temperature increase.The energy available depends on what happens to the water produced from thecombustion of the hydrogen. If the water remains as a gas, then it cannotrelease the heat of vaporisation, thus producing the Nett Calorific Value.If the water were condensed back to the original fuel temperature, thenGross Calorific Value of the fuel, which will be larger, is obtained.

The calorific values are fairly constant for families of HCs, which is notsurprising, given their fairly consistent carbon:hydrogen ratios. For liquid( l ) or gaseous ( g ) fuel converted to gaseous products - except for the2-methylbutene-2, where only gaseous is reported. * = Blending Octane Numberas reported by API Project 45 using 60 octane base fuel, and the numbersin brackets are Blending Octane Numbers currently used for modern fuels.Typical Heats of Combustion are [36]:-

Fuel State Heat of Combustion Research MotorMJ/kg Octane Octane

n-heptane l 44.592 0 0g 44.955

i-octane l 44.374 100 100g 44.682

toluene l 40.554 124* (111) 112* (94)g 40.967

2-methylbutene-2 44.720 176* (113) 141* (81)


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Because all the data is available, the calorific value of fuels can beestimated quite accurately from hydrocarbon fuel properties such as thedensity, sulfur content, and aniline point ( which indicates the aromaticscontent ).

It should be noted that because oxygenates contain oxygen that cannot provide energy, they will have significantly lower energy contents.They are added to provide octane, not energy. For an engine that can beoptimised for oxygenates, more fuel is required to obtain the same power,but they can burn slightly more efficiently, thus the power ratio is notidentical to the energy content ratio. They also require more energy tovaporise.

Energy Content Heat of Vaporisation Oxygen ContentNett MJ/kg MJ/kg wt%

Methanol 19.95 1.154 49.9Ethanol 26.68 0.913 34.7MTBE 35.18 0.322 18.2ETBE 36.29 0.310 15.7TAME 36.28 0.323 15.7Gasoline 42 - 44 0.297 0.0

Typical values for commercial fuels in megajoules/kilogram are [37]:-Gross Nett

Hydrogen 141.9 120.0Carbon to Carbon monoxide 10.2 -Carbon to Carbon dioxide 32.8 -Sulfur to sulfur dioxide 9.16 -Natural Gas 53.1 48.0Liquified petroleum gas 49.8 46.1Aviation gasoline 46.0 44.0Automotive gasoline 45.8 43.8Kerosine 46.3 43.3Diesel 45.3 42.5Obviously, for automobiles, the nett calorific value is appropriate, as thewater is emitted as vapour. The engine can not utilise the additional energyavailable when the steam is condensed back to water. The calorific value isthe maximum energy that can be obtained from the fuel by combustion, but thereality of modern SI engines is that thermal efficiencies of only 20-40% maybe obtained, this limit being due to engineering and material constraintsthat prevent optimum thermal conditions being used. CI engines can achievehigher thermal efficiencies, usually over a wider operating range as well.Note that combustion efficiencies are high, it is the thermal efficiency ofthe engine is low due to losses. For a water-cooled SI engine with 25%useful work at the crankshaft, the losses may consist of 35% (coolant),

33% (exhaust), and 12% (surroundings).4.10 What are the gasoline specifications?

Gasolines are usually defined by government regulation, where properties andtest methods are clearly defined. In the US, several government and statebodies can specify gasoline properties, and they may choose to use or modifyconsensus minimum quality standards, such as American Society for TestingMaterials (ASTM). The US gasoline specifications and test methods are listed


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until significant oxygen uptake is measured.

4.10.9 Water ToleranceHighest temperature that causes phase separation of oxygenated fuels.The limits vary according to location and month. For Alaska - North of 62latitude, it changes from -41C in Dec-Jan to 9C in July, but remains 10C all

year in Hawaii.

Because phosphorus adversely affects exhaust catalysts, the EPA limitsphosphorus in all gasolines to 0.0013g P/L.

As well as the above, there are various restrictions introduced by the CleanAir Act and state bodies such as California's Air Resources Board (CARB)that often have more stringent limits for the above properties, as well asadditional limits. More detailed descriptions of the complex regulationscan be found elsewhere [16,41,42] - I've just included some of the majorchanges, as some properties are determined by levels of permitted emissions,eg the toxics reduction required for fuel that has the maximum permittedbenzene (1.0%), means total aromatics are limited to around 27%. There havebeen some changes in early 1996 to the implementation timetable, and thefollowing timetable has not yet been changed.

The Clean Air Act also specifies some regions that exceed air qualitystandards have to use reformulated gasolines (RFGs) all year, startingJanuary 1995. Other regions are required to use oxygenated gasolines forfour winter months, beginning November 1992. The RFGs also containoxygenates. Metropolitan regions with severe ozone air quality problems mustuse reformulated gasolines in 1995 that;- contain at least 2.0 wt% oxygen,reduce 1990 volatile organic carbon compounds by 15%, and reduce specifiedtoxic emissions by 15% (1995) and 25% (2000). Metropolitan regions thatexceeded carbon monoxide limits were required to use gasolines with 2.7 wt%oxygen during winter months, starting in 1992.

The 1990 Clean Air Act (CAA) amendments and CARB Phase 2 (1996)specifications for reformulated gasoline establish the following limits,compared with typical 1990 gasoline. Because of a lack of data, the EPAwere unable to define the CAA required parameters, so they instituteda two-stage system. The first stage, the "Simple Model" is an interimstage that run from 1/Jan/1995 to 31/Dec/1997. The second stage, the"Complex Model" has two phases, Phase I (1995-1999) and Phase II (2000+),and there are different limits for EPA Control Region 1 (south) and ControlRegion 2 (north). Each refiner must have their RFG recertified to theComplex model prior to the 1/Jan/1998 implementation date. The followingare some of the criteria for RFG when complying on a per gallon basis, moredetails are available elsewhere, including the details of the baseline fuelcompositions to be used for testing [16,41,42,43,43a].

1990 Clean Air Act CARBSimple Complex Phase 2

I II Limit Averagebenzene (max.vol.%) 2 1.00 1.00 1.00 1.00 0.8oxygen (min.mass %) 0.2 2.0 2.0 2.0 1.8 -

(max.mass %) - 2.7 - - 2.2 -sulfur (max.mass ppm) 150 no increase - - 40 30aromatics (max.vol.%) 32 toxics reduction - - 25 22


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olefins (max.vol.%) 9.9 no increase - - 6.0 4.0reid vapour pressure (kPa) 60 55.8 (north) - - 48.3 -(during VOC Control Period) 49.6 (south)50% evaporated (max.C) - - - - 98.9 9390% evaporated (max.C) 170 - - - 148.9 143VOC Reductions - Region I (min.%) 35.1 27.5 - -

(VOC Control Period only) - Region II (min.%) 15.6 25.9 - -NOx Reductions - VOC Control Period (min.%) 0 5.5 - -- Non-VOC Control Period (min.%) 0 0 - -

Toxics Reductions (min.%) 15.0 20.0 - -

These regulations also specify emissions criteria. eg CAA specifies noincrease in nitric oxides (NOx) emissions, reductions in VOC by 15% duringthe ozone season, and specified toxins by 15% all year. These criteriaindirectly establish vapour pressure and composition limits that refinershave to meet. Note that the EPA also can issue CAA Section 211 waivers thatallow refiners to choose which oxygenates they use. In 1981, the EPA alsodecided that fuels with up to 2% weight of oxygen ( from alcohols and ethers(except methanol)) were "substantially similar" to 1974 unleaded gasoline,and thus were not "new" gasoline additives. That level was increased to2.7 wt% in 1991. Some other oxygenates have also been granted waivers, egethanol to 10% volume ( approximately 3.5 wt% ) in 1979 and 1982, andtert-butyl alcohol to 3.5 wt% in 1981. In 1987 and 1988 further waiverswere issued for mixture of alcohols representing 3.7% wt of oxygen.

4.11 What are the effects of the specified fuel properties?

VolatilityThis affects evaporative emissions and driveability, it is the property thatmust change with location and season. Fuel for mid-summer Arizona would bedifficult to use in mid-winter Alaska. The US is divided into zones,according to altitude and seasonal temperatures, and the fuel volatility isadjusted accordingly. Incorrect fuel may result in difficult starting incold weather, carburetter icing, vapour lock in hot weather, and crankcaseoil dilution. Volatility is controlled by distillation and vapour pressurespecifications. The higher boiling fractions of the gasoline have significanteffects on the emission levels of undesirable hydrocarbons and aldehydes,and a reduction of 40C in the final boiling point will reduce the levels ofbenzene, butadiene, formaldehyde and acetaldehyde by 25%, and will reduceHC emissions by 20% [44].

Combustion CharacteristicsAs gasolines contain mainly hydrocarbons, the only significant variablebetween different grades is the octane rating of the fuel, as most otherproperties are similar. Octane is discussed in detail in Section 6. Thereare only slight differences in combustion temperatures ( most are around

2000C in isobaric adiabatic combustion [45]). Note that the actualtemperature in the combustion chamber is also determined by other factors,such as load and engine design. The addition of oxygenates changes thepre-flame reaction pathways, and also reduces the energy content of the fuel.The levels of oxygen in the fuel is regulated according to regional airquality standards.

StabilityMotor gasolines may be stored up to six months, consequently they must not


20/25


21/25

HOW CAN I CHECK FOR WATER IN GASOLINE? by RALPH (3/6/2004)

Why is turning on of cellphones prohibited while filling up? by charlie(3/27/2004)

WHAT IS THE CALORIFIC VALUE FOR AUTOMOBILE GAS by

PRINCEWILL (9/9/2003)

I recently spilled gasoline in my car, how can I get the smell out? by Ashley(8/29/2003)

wich gasoline provides better fuel economy by noel cura (11/12/2003)

Is there any regulations that pertains to gasoline dispenser versus diesel

dispensers at... by dumb and dummer (10/8/2003) What is the % of water in gasoline?? I was told that gasoline is 25% water.

Is... by kgf (4/11/2004) what is the composition of pure tertiary butyl alcohol to produce

isobutylene? by umi (11/3/2003) What is the freezing point of unleaded gasoline? by Brad (1/17/2004)

how much does a gallon of diesel fuel weigh by ryan walker (12/30/2003)

I am looking for information on the addition of xylene and distillates as itapplies to... by Garey Porter (3/26/2004)

What is the typical composition of gasoline at the pump in China. I am

looking for the... by Shelto (7/16/2003) What ingredient is added to enhance the smell of auto gasoline? Aviation

gasoline... by Dick Siano (2/23/2004) I wanted to a testing using a petrol or gasoline. Method, I have to put the

petrol inside... by hasbullah (3/8/2004) what is the function of the egr valve? Can it be repaired or does it need to

be replaced? by willycox (11/6/2003) What are the emissions from various octanes? Does using the wrong

octane affect emissions?... by G-train (6/30/2003) what is the vapor pressure and flammable range of gasoline by tom g

(10/6/2003) What is the scientific name for gasoline. what is it's history and who

discovered... by don\\\'t (11/21/2003) What is the chemical formula of gasoline? by ChuRrO (3/8/2004)

what does gasoline turn into after sitting in a tank for 10+ years? by #1 tech

bull (11/8/2003) How do I get rid of the smell of gasoline that spilled inside my car? by

Noname (11/5/2003) Is gasoline considered an explosive or a flammable liquid? What's the

difference? by rickshane (7/25/2003) How many gasoline companies or distributors are in the USA? What oil

companies are... by swervn (3/12/2004) how do you find the miles per gallon of automobiles? by kerry (11/5/2003)

What is the differance between automotive gasoline and (white

gas?)coleman fuel and what... by tripple t (3/23/2004) What is the average (v/v)percentage of Xylenes in North American
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22/25

gasoline? by Bernard McCue (8/25/2003) I know that a local gas station is falsely advertising the octane levels in

their... by jonathan (7/1/2003) If i purchase 100LL Av gas what is the equivalent automotive rating?

Thanks Willie by Willie (11/18/2003)

I've read 6.13 and 6.14 and low octane levels then what the car is rated forwill cause... by nosey (10/29/2003)

WHAT IS THE SHELF LIFE OF GASOLINE? by TONY (8/18/2003)

What are some theories that related to gasoline station? by Rhein

(1/11/2004) Is there a complete list of chemicals in gasoline? I am looking for 2-

Butanone (MEK)... by Bruce (1/24/2004) Is the refining process more expensive because consumers are offered 3

octane choices at... by JMash (3/16/2004) Exactly what percent of gasoline (standard, unleaded that you buy at a

pump) is made up of... by Melanie (10/12/2003)

what is exactly meant by negative temperature region? by pallavi (8/9/2003) How many kWh of energy are there in 1L of gasoline? by gs (11/8/2003)

What happens if you accidently put gasoline into a diesel tank? what would

be the... by Bob Johnson (1/28/2004) When was the last time gasoline was restricted and what were the causes

of this crisis? by Shelly (9/26/2003) All other variables being equal, is it true that a lower octane level gasoline

will have... by EDWARD (8/23/2003) On a natural gas well not fitted with a pump jack, is there a method other

than a BTU... by Ralph G. Reser (8/30/2003) What is the chemical composition of diesel? by Tanja (1/8/2004)

How does manganese improve the octane number of gasoline & otherfuels? by Erum Qayyum (9/14/2003)

how manganese in MMT improves the octane rating of gasoline?

[email protected] by daptiyeh (9/14/2003) Why does the last quarter of a tank of gas seem to burn off more quickly

than the rest of... by gomer (12/22/2003) how do we get our gasoline, and why does it cost so much? Will the price

ever go down? by kris (4/15/2004) What is gasoline made of? by viper (12/9/2003)

What is the chemical compound that can melt rubber cement? by Tess

(1/16/2004) My mother inherited a 1964 Jeep from her father and is being told by her

mechanic that it... by Cathy (4/7/2004) I spilled gasoline in my car and have tried everything under the sun to

remove and have... by Dawn (12/31/2003) What is the percentage (v/v) of Xylene in gasoline? by Mac (8/25/2003)

Where does gasoline come from? by Angelika (2/23/2004)

what happens when you put diesal fuel in your car when its not one by
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23/25

dreamer0010 (8/5/2003) When ignited by the sparkplug, does a higher octane fuel burn with a

progressive flame... by Hutch (7/16/2003) Why are the hydrocarbons considered good for combustion? Why are they

a good source for... by Magnumb69 (9/25/2003)

What types of molecules are present in unleaded and leaded gasoline? byjack (2/24/2004)

Has the cost of gasoline been equal to the cost of anything in the past threedecades? Of... by Jack Powers (3/8/2004)

Please explain the reasons for the significant peaks and valleys in the price

of petrol... by catgorman (3/10/2004) What is the country of origin, the one the oil wells are in, that the crude oil

refined in... by thekrout49 (12/30/2003) What affect that wind speed & direction, octane rating, height in sea level,

and topograph... by frank (4/14/2004) what happens if you use unleaded when you are supposed to use leaded

gas? by katpet (7/18/2003) Which European countries use MMT as an fuel additive? How much is used

in each country or... by Tom Returned (2/12/2004) could gas be semi-frozen to isolate dilutants(so as to be removed)to purify

the mixture... by adam (3/5/2004) The correct name for the (RON+MON)/2 formula is the "antiknock index",

and it remains the... by Karl (2/27/2004) gasoline is definitely a vital fluid in all over the world. it is as vital to the

economy... by azah (8/4/2003) what are the values of the following parameters for diesel and gasoline :

specific... by moufid (1/20/2004) Is the lead content of various gasoline stations differ from each other even if

they are... by nesty (2/14/2004) Is there any known system of gasoline tax rebate around the world? by

Ellen (10/25/2003) Is there any effect of magnetic field on gasoline molecules? can magnetic

field applied at... by meeta (11/14/2003) Is there any difference between gas at a Shell or Chevron station to the gas

at a corner... by r2a2 (7/6/2003) I would like to know if I can remove the alcohol from my mogas by adding

water and shaking... by mogas (12/1/2003) who invented race car fuel? by steph (2/29/2004)

what is formula for gasoline? by usama (4/23/2004) What happens if you pit diesel in an unleaded car, will it damage the

engine? by kerby (11/22/2003) I understand that Natural Gas prices are dependent on the Crude Oil prices

and is directly... by ksssarma (11/15/2003) Why must gasoline whipped in winter to a northern state such as

Minnesota, be different... by L.L. (3/11/2004)
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25/25

beamen (7/7/2003) Why would anyone use DMDA as an additive in gasoline? by Bill (Gumby)

(3/13/2004) How is gasoline made, what's the process it goes through and what are the

chemicals used? by Coni (11/20/2003)

I put gas in my van that had "phase contamination". What problems can beexpected from... by Jean Parker (3/7/2004)

Why should we still keep using gasoline? by Haigster (12/17/2003)

What products are made from a barrel of Crude? Thanks by Bill (3/7/2004)

I am looking for the formula of gasoline, what makes it up and the chemical

reactions by steph (2/22/2004) How much does 1 gallon of Gasoline weigh? by jim (8/19/2003)

i have a 1982 honda civic 2 door. the oil and gas is mixing together. the oil

smell like... by eric (10/24/2003) When gas is put into a car what happens to the gas as the car is driven and

what has the... by Nelly (11/2/2003) how do rid my car of the noxious fumes of the gasoline that spilled in my

back seat... by mark (10/1/2003) I live and work in Cambodia where I travel extensively via dirt bike. I buy

gasoline in... by Dave in Paradise (1/27/2004) what are the various methods of estimating BMCI in CBFS(Carbon block

feed stock) by ramky (7/5/2003)

Other questions awaiting answers: 14857 questions related to other FAQs 2575 general questions

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