How you convert premium gas engine to regular gas?

Answer 1

Reducing an engines need for higher octane fuel requires lowering the static compression ratio of the engine(changing heads and/or pistons) and retarding the ignition somewhat. Cars with a static compression ratio of 9:1 or less can run on "regular" with just dialing back the ignition timing and not pushing the engine hard. Reducing compression ratios or retarding timing will cost you power however, and may cause your engine to run less efficiently(higher emissions). on modern computer controlled cars, changing the ignition timing is far more difficult than on a vehicle with a standard distributor.