100LL AVGAS is far from "low lead". While the LL indicates that, it is simply a designator that came into play decades ago. AVGAS 100LL has a rather high lead content compared to what automotive fuels had. If you have oxygen sensors in your exhaust, you do NOT want to run AVGAS! It will quickly coat and ruin them.
The difference in low octane gasoline compared to high octane gasoline is not just in the additive package. Far from it. Lower octane fuels have more unstable hydrocarbons. The refining process can continue to lower those unstable hydrocarbons, which nets the higher octane fuels. Vapor pressure, and additives to adjust it, are added to both along with other additives to improve different properties of gasoline. But high octane fuel is NOT the same fuel as low octane before the additive packages are introduced. Most would assume there is regular, mid grade, and premium fuel in tanks below ground that is delivered from the refinery. Actually there is low octane and high octane. Blend pumps then blend these two grades to form the mid grade you buy.
Because high octane fuel is refined to a higher standard, there are some cases where it can produce more horsepower due to the energy content ( BTU per pound of fuel ). But it is NOT because of the octane rating, again simply because of the higher energy contained. In many cases lower octane fuel will actually make more horsepower as lower octane fuel can burn quicker and reach optimum cylinder pressure quicker. But this is very hard to test and prove, a dyno engine setup would be the only way to really prove it. It has been done, and the differences are very minor and not always repeatable across brands and runs of refined fuel. The only reason to run higher octane fuel is to get the most out of an engine designed for it. If not designed for high octane fuel, it is usually a waste of money as and improvement is likely a placebo effect.
We do agree that race fuel smell is intoxicating!
At our Shell fuel station that we had up until the early 2000s we did not blend reg and premium to get mid grade and I never seen a station that did that. We had 3 storage tanks that had the 3 grades.
In premium fuel you donít just get the higher octane from certain brands, as you say you get additives that clean fuel systems and help to have a better burn in the combustion chamber. Thus you shouldnít have to buy all the cleaning additives etc to your tank to keep injectors clean etc. Also up in Canada most or your premium fuels from the majors donít contain ethanol. Big advantage there.
When I was racing sleds in the WSA I ran Shell premium and the brand I was riding 2 stroke oil, plus I was running stock sleds, I could run a jet size leaner than other guys running the same sled. Then I had an engine pulled apart at factory and they had never seen an engine so clean.
One other thing about additives in fuels. Look at F1 they use to run special fuels from fuel company sponsors, these special blends could add 100 hps or more, but 45 gallon drums of the stuff could cost $100,000 or more. To cut cost FIA outlawed it. Now they run close to pump gas. I would say the additives do make a difference in premium.
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