Quote:
Originally Posted by Ecky
Generally you'll see either "Premium fuel recommended" or "Premium fuel required" under the gas cap door. I understand the difference is that "recommended" are vehicles whose knock sensors will pull timing and safely operate with lower octane gas, while "required" are those that will be damaged by running regular.
Out of curiosity, is there any advantage to re-turning a vehicle where premium fuel is only recommended?
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Oftentimes, the timing curve is pretty conservative and some cars can get away with a smaller constant retard on timing than the PCM retards timing upon knock detection...
Example, if my car could handle 24* of timing advance running wide open on 91octane but pulls 12* out when it detects knock, it might run better on regular if timing were backed off to 19* of advance to eliminate knock... would yield more advance on the cheaper fuel...