Quote:
Originally Posted by FourBinLabs
Well, I read the whole thing. I'd say you were spot on Mr. NachtRitter. Thanks for the link and re recommending it after I skipped over it the first time.
Octane rating is not related to when a fuel preignites or auto ignites (per se), it's actually measuring the probability of molecules being broken down into other molecules that are more likely to auto ignite.
it takes more heat to auto ignite diesel fuel than gasoline, however diesel fuel either A) breaks down into readily auto ignited compounds easier/faster than gasoline when exposed to high heat and pressure or B) breaks down into compounds that are more auto ignitable than what gasoline breaks down into.
It makes sense now. I think a lot of the confusion here was many terms that were being used in a less than 100% accurate manner.
If you go on to read further, it does state that it does not hurt to use lower octane fuel in a vehicle than what is specified if the vehicle does not knock (although a knock sensor would prevent you from knowing this). High elevation and low temperatures also allow the use of lower octane. If the vehicle is not knocking, then lowering the octane is no problem.
If you can advance your timing with the same octane you used before, you decreased your margin for error and reap the rewards of better mileage & torque. Buying lower octane for cheaper saves $, and causes no harm if it isn't making the vehicle knock. So diesel lowering the octane rating isn't necessarily bad.
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Good summary.... and I definitely agree that the terms are often not being used correctly.
Back to the original discussion...
