FAQ: Automotive Gasoline

[cpostis]

OK guys, wanna know a little about gasoline....

[IMG]VeryInteresting by Charles Postis, on Flickr[/IMG]

Please note, this FAQ is from an article last revised in 1995. However, this is the most comprehensive information I have found on the subject. Although the author has directed his thoughts to the "layman", apparently he is/was a chemist or other professional and much of the information is "over my head".

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

Here is the link to the complete article:

Automotive Gasoline FAQ

[boscoe99]

I opened and skimmed through the article. My eyes are glazed over. I can not see.

"This FAQ intended to help readers choose the most appropriate fuel"

Why wouldn't someone just use the gasoline that the engine maker tells them to use? Eg gasoline with no more than 10% added ethanol with an octane rating of XZ or more.

[robert graham]

I'm glad this was directed to the"layman" type readers so all us average mechanical meatballs could really understand it!....pretty heavy duty info!!!

[scofflaw]

Like said.....there are no choices.....more than half the country don't even have a non eth option

[pstephens46]

Half the country cannot get non-ethanol gasoline?

Yes, Yamaha tells us it is ok to use E-10. It is clearly stated in the Operators and Service Manual. I suspect they want to sell engines in every state, including CA.

Can E-10 create issues with marine outboards?

[boscoe99]

Any gasoline can create issues with any engines. Moreso with outboard motors it seems due to their propensity to sit unused for long periods of time. In generally hotter and more humid climes.

E10 can make things a bit worse.

In the 1950's people (my dad being one) were having problems with lawn motor engines after they had sat idle for many months during the winter. His boat motors also.

Piston engine powered airplanes are alleged to be using the most stringent quality of gasoline known to be available to man. They have gasoline issues when airplanes sit on the tarmac unused for long periods of time.

[pstephens46]

Any gasoline can create issues with any engines. Moreso with outboard motors it seems due to their propensity to sit unused for long periods of time. In generally hotter and more humid climes.

E10 can make things a bit worse.

In the 1950's people (my dad being one) were having problems with lawn motor engines after they had sat idle for many months during the winter. His boat motors also.

Piston engine powered airplanes are alleged to be using the most stringent quality of gasoline known to be available to man. They have gasoline issues when airplanes sit on the tarmac unused for long periods of time.

Letting an airplane sit unused also makes for a half-assed pilot as well.

The outboard manufacturers tell us they are lobbying furiously against the coming shift to E-15 due to the issues it will create with motors. So E-10 is safe and E-15 is the end of the world? I have had no issues with E10 in my boat as I have not ever used it. I used lots of ethanol in my various lawn equipment. Every year I would be rebuilding/cleaning carbs, replacing fuel lines and bulbs etc. I switched to marine gas and haven't had any fuel issues since.

[pstephens46]

Like said.....there are no choices.....more than half the country don't even have a non eth option

Other than CA, look like you can find non-ethanol in just about any state.
Ethanol-free gas stations in the U.S. and Canada

[fairdeal]

I've used only E-10 since 2011 -

first in a 2006 F90, then in my F225TXRD.

So far I have had just one problem;

the F90 had been rigged with a "Mercury OEM" fuel bulb/hose -

a strange silver colored tubing with a clear inner liner.

After a few months of exposure to E-10, the plastic liner turned into crumbly brown chips,

and some semi-soluble schmutz that made it to the injector baskets.

[cpostis]

Any gasoline can create issues with any engines. Moreso with outboard motors it seems due to their propensity to sit unused for long periods of time. In generally hotter and more humid climes.

E10 can make things a bit worse.

In the 1950's people (my dad being one) were having problems with lawn motor engines after they had sat idle for many months during the winter. His boat motors also.

Piston engine powered airplanes are alleged to be using the most stringent quality of gasoline known to be available to man. They have gasoline issues when airplanes sit on the tarmac unused for long periods of time.

Well, looks like avgas is going through some changes as well!

Have a look:

History of AVGAS Grades
Avgas is gasoline fuel for reciprocating piston engined aircraft. As with all gasolines, avgas is very volatile and is extremely flammable at normal operating temperatures. Procedures and equipment for safe handling of this product must therefore be of the highest order.
Avgas grades are defined primarily by their octane rating. Two ratings are applied to aviation gasolines (the lean mixture rating and the rich mixture rating) which results in a multiple numbering system e.g. Avgas 100/130 (in this case the lean mixture performance rating is 100 and the rich mixture rating is 130).
In the past, there were many different grades of aviation gasoline in general use e.g. 80/87, 91/96, 100/130,108/135 and 115/145. However, with decreasing demand these have been rationalised down to one principle grade, Avgas 100/130. (To avoid confusion and to minimise errors in handling aviation gasoline, it is common practice to designate the grade by just the lean mixture performance, i.e. Avgas 100/130 becomes Avgas 100).
Some years ago, an additional grade was introduced to allow one fuel to be used in engines originally designed for grades with lower lead contents: this grade is called Avgas 100LL, the LL standing for 'low lead'.
All equipment and facilities handling avgas are colour coded and display prominently the API markings denoting the actual grade carried. Currently the two major grades in use internationally are Avgas 100LL and Avgas 100. To ease identification the fuels are dyed i.e. Avgas 100LL is coloured blue, while Avgas 100 is coloured green.
Very recently a new Avgas grade 82 UL (UL standing for unleaded) has been introduced. This is a low octane grade suitable for low compression engines. It has a higher vapour pressure and can be manufactured from motor gasoline components. It is particularly applicable to those aircraft which have STCs to use automotive gasoline.

[Jason2tpa]

Interesting article. I skimmed through most except the section about octane, which caught my attention. I had thought using a higher octane fuel would produce a corresponding higher engine performance. Apparently not so. This article states so long as you're using the manufacturers recommended optimal octane fuel, which for most autos is 87, the engine is performing at its highest potential. Using a 91 octane in a 87 octane auto gets you nothing except less $$ in your pocket.

The ethanol--non ethanol debate seems to have no finality. No dispute ethanol fuel isn't so good for marine engines. However, for instance, if the 10 ethanol fuel doesnt remain stagnant in the tank for an extended period of time, and a fuel stabilizer is added with every fill up...how could one justify the ethanol fuel will cause a problem? It's not in the tank long enough to cause issues, no?

[boscoe99]

The avgas using community is in a quandry because the EPA wants all leaded gasoline to be done away with. Right now they are using 100LL (for 100 octane low lead) but it has plenty of lead in it, despite the name. Unfortunately, lead is the only substance currently available that can result in gasoline having the needed octane rating for airplane motors to produce their rated power. At a reasonable price.

Big piston engine motors can't function on just 82 octane. Puddle jumpers yes, but not a six cylinder big bore motor producing 350 HP.

In the good old days when various octane rated avgas was available it was dyed so as to colour code it. For some strange reason I enjoyed seeing red, blue, green and purple gasoline. It also had a good smell to it when burned.

I really like the smell of Jet A being burned. Wish I could afford a kerosene burning something or other.

[cpostis]

Some specific information for review and comments:

What are the problems associated with storing fuel for a prolonged period of time?

Seems to me it is “gumming” of the fuel, loss of octane, and water intrusion in the fuel.

As others have said, the best resolution is to store the fuel properly and take precautions in treating/draining your engine of fuel during periods of prolonged storage. An ounce of prevention is worth a pound of cure!

Here are excerpts from the article concerning this:

8.6 What is "stale" fuel, and should I use it?
"Stale" fuel is caused by improper storage, and usually smells sour. The gasoline has been allowed to get warm, thus catalysing olefin decomposition reactions, and perhaps also losing volatile material in unsealed containers. Such fuel will tend to rapidly form gums, and will usually have a significant reduction in octane rating. The fuel can be used by blending with twice the volume of new gasoline. Some stale fuels can drop several octane numbers, so be generous with the dilution.

8.7 How can I remove water in the fuel tank?
If you only have a small quantity of water, then the addition of 500mls of dry isopropanol (IPA) to a near-full 30-40 litre tank will absorb the water, and will not significantly affect combustion. Once you have mopped up the water with IPA. Small, regular doses of any anhydrous alcohol will help keep the tank dry. This technique will not work if you have very large amounts of water, and the addition of greater amounts of IPA may result in poor driveability.
Water in fuel tanks can be minimised by keeping the fuel tank near full, and filling in the morning from a service station that allows storage tanks to stand for several hours after refilling before using the fuel. Note that oxygenated gasolines have greater water solubility, and should cope with small quantities of water.

Boscoe, this is for you:
6.19 Are aviation gasoline octane numbers comparable?
Aviation gasolines were all highly leaded and graded using two numbers, with common grades being 80/87, 100/130, and 115/145 [70]. The first number is the Aviation rating ( aka Lean Mixture rating ), and the second number is the Supercharge rating ( aka Rich Mixture rating ). In the 1970s a new grade, 100LL ( low lead = 0.53mlTEL/L instead of 1.06mlTEL/L) was introduced to replace the 80/87 and 100/130. Soon after the introduction, there was a spate of plug fouling, and high cylinder head temperatures resulting in cracked cylinder heads [71]. The old 80/87 grade was reintroduced on a limited scale. The Aviation rating is determined using the automotive Motor Octane test procedure, and then corrected to an Aviation number using a table in the method - it's usually only 1 - 2 Octane units different to the Motor value up to 100, but varies significant above that eg 110MON = 128AN.
The second Avgas number is the Rich Mixture method Performance Number ( PN - they are not commonly called octane numbers when they are above 100 ), and is determined on a supercharged version of the CFR engine which has a fixed compression ratio. The method determines the dependence of the highest permissible power ( in terms of indicated mean effective pressure ) on mixture strength and boost for a specific light knocking setting. The Performance Number indicates the maximum knock-free power obtainable from a fuel compared to iso-octane = 100. Thus, a PN = 150 indicates that an engine designed to utilise the fuel can obtain 150% of the knock-limited power of iso-octane at the same mixture ratio. This is an arbitrary scale based on iso-octane + varying amounts of TEL, derived from a survey of engines performed decades ago. Aviation gasoline PNs are rated using variations of mixture strength to obtain the maximum knock-limited power in a supercharged engine. This can be extended to provide mixture response curves which define the maximum boost ( rich - about 11:1 stoichiometry ) and minimum boost ( weak about 16:1 stoichiometry ) before knock [71].
The 115/145 grade is being phased out, but even the 100LL has more octane than any automotive gasoline.

[scofflaw]

Other than CA, look like you can find non-ethanol in just about any state.
Ethanol-free gas stations in the U.S. and Canada

Look closer at that map, look at where it's being sold. Unavailable to big boat owners unless it's being sold at a marina.

[pstephens46]

Other than CA, IL and maybe NY and NJ, looks to be very available in coastline marinas. Where you would find "big" boats. You said half the country.....

Another reason not to live in one of the bleeding heart states.....