Fuels- everything you didn’t need to know

Since the very beginning of time, mankind has been on the quest for FUEL, probably, indisputably the number one invention of all time. Our use of fuel started in prehistoric times as a way to heat our cave and then to cook our food, then to power our motorcycles (sorry cavemen!)

Without Fuels to produce heat, we wouldn’t have any metal, so we would still be in the Stone Age. Without Fuel NONE of today’s modern age society would exist as we know it. We use Fuels for so many things that if you took a few minutes to think about it you would realize that we couldn’t live without them. Take that you greenie hypocrites!

Gasoline was not invented; it is a natural by-product of the petroleum industry, kerosene being the principal product. Gasoline is produced by distillation, the separating of the volatile, more valuable fractions of crude petroleum. However, what was invented were the numerous processes and agents needed to improve the quality of gasoline making it a better more stable fuel. One thing virtually every fuel has in common is that by itself, it is not combustible- they require an Oxidizer. The most easily obtained oxidizer we have available to us is our AIR and it’s oxygen component. Internal Combustion engines mix fuel and air enabling the combustion process. With a spark at the right time we are able to make power.

Now, the real reason for this article- to discuss motor fuels and their effect on our Yamaha Engines. Probably the number one question I get asked is- “What type of motor fuel is best in my motorcycle?” Well let’s first look at the Components of today’s modern fuels.

Today’s Fuels are filled with lots of stuff, but they all start with a base petroleum distillate, and then other things are added. Some compounds added are Detergents (to help keep the combustion tracts clean) and oxygenates (which are supposed to reduce some of the harmful compounds emitted by the combustion process). These additives have an overall effect on the one thing we are all most concerned about- the Octane rating.

The Octane rating of a gasoline is a measurement of the burn rate of the fuel. In internal combustion engines, the compressed gasoline-air mixtures have a tendency to ignite prematurely rather than burning smoothly. This creates engine pre- ignition or knock, a characteristic rattling or pinging sound in one or more cylinders. The octane number of gasoline is a measure of its resistance to knock. The octane number is determined by comparing the characteristics of a gasoline to isooctane (2,2,4-trimethylpentane) and heptanes. Isooctane is assigned an octane number of 100. It is a highly branched compound that burns smoothly, with little knock. On the other hand, heptane is given an octane rating of zero. It is an unbranched compound and knocks badly. By averaging the burn rate of a particular fuel, we can determine its octane rating. The one missing link is the consistency of a particular fuels quality to maintain this rating. Lot’s of stuff affects a fuels quality, but nothing as much as the current trend of OXYGENATES added to fuel. The most common Oxygenate used today is Alcohol, and this really messes with fuel quality as the alcohol being used absorbs water from the air and we all know gas and water don’t like each other…

It is important to note that the theoretical energy content of gasoline when burned in air is only related to the hydrogen and carbon contents. Octane rating is not fundamentally related to the energy content, and the actual hydrocarbon and oxygenate components used in the gasoline will determine both the energy release and the anti-knock rating. This is the main reason Racing Gas does not provide more power in a stock engine.

Can I run racing gas in my bike? Yes, you could run unleaded racing gas, but it is a waste of money. You will not make more power nor will you get better mileage- actually probably worse mileage.

Why is Racing Gas so expensive? Because it is a more highly refined fuel. This makes the fuel more stable and resistant to pre-ignition. The Stability is important when we ask a highly tuned engine to run “on the edge” because even a small pre- ignition event can destroy a lot of parts. One way we test our racing gas is with a hydrometer. We measure the fuels specific gravity. This is a measurement of the density of the fuel. Racing gasolines are typically denser than pump gas. When run through a carbureted engine set up for pump gas, the racing gas will typically be too rich for the pump gas jetting.

When gasoline is left for a period of time, gums and varnishes may build up and precipitate in the gasoline, causing "stale fuel". This will cause gums to build up in the fuel tank, lines, and carburetor or fuel injection components making it harder to start the engine. Motor gasoline may be stored up to 60 days in an approved container. If it is to be stored for a longer period of time, a fuel stabilizer may be used. This will extend the life of the fuel to about 1–2 years, and keep it fresh for the next uses. Fuel stabilizer is commonly used for small engines such as lawnmower and tractor engines to promote quicker and more reliable starting. We recommend that you keep gasoline containers and tanks more than half full and properly capped to reduce air exposure, to avoid storage at high temperatures, to run an engine for ten minutes to circulate the stabilizer through all components prior to storage, and to run the engine at intervals to purge stale fuel from the carburetor.

What about “Avgas” or Aviation Gasoline? What about it- it is MADE FOR AIRPLANES. Avgas has a lower and more uniform vapor pressure than automotive gasoline, which keeps it in the liquid state at high-altitude, preventing vapor lock. The particular mixtures in use today are the same as when they were first developed in the 1950s and 1960s, and therefore the high-octane ratings are achieved by the addition of tetra-ethyl lead (TEL), a highly toxic substance that was phased out for car and motorcycle use in most countries in the late 20th century. Don’t run it in your bike. First, you don’t need to, second the lead will kill your catalytic converter.

So, what should you do for your Yamaha engine?

1. Run the highest pump octane number available (usually 92) more octane is not necessary, but less is bad.
2. Run a name brand fuel-  preferably from the same station
3. Don’t use Octane Boosters or other “Power Additives”
4. Don’t let your bike sit for more than 60 days without putting some Yamaha Fuel Conditioner and Stabilizer in the fuel system

Happy Riding!
Dr Jay

What About E-10 Fuels? - Fuels Continued