Sorry - he has it entirely wrong. High octane fuel does not burn more slowly or expect higher combustion temperatures than regular gasoline - it just has a slightly higher threshold of switching from propagating ignition by flame front to pressure front when the fuel-air vapor is compressed. This translates to a higher ignition point but has nothing inherently to do with energy density, flame propagation rate or completeness of combustion.
Mike
My Acura manual requires high octane gas but says that low octane can be substituted with a resulting loss in horsepower. I don't care about the power I want fuel economy.
When I first got my car 5 years ago, I tracked my mileage using the higher octane and then switched to low octane and tracked that mileage as well. I had a slight decrease in mpg with the lower octane but it was more economical because of the difference in price with premium.
As the price of gas has gone up to close to $3 per gallon the previous economic benefit using low octane may no longer be true. I am using high octane again and tracking the mpg to see if I get the same mpg I used to.
My first tank gave me a improvement of 9% per gallon. Since the price difference from low to high octane is $0.20 any time the price of low octane gas is higher than $2.22 (0.20/9%) it is cheaper to use high octane gas.
One tank is not enough to make me believe I will have 9% improvement but tracking it over time will prove or disprove the benefit.
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.