This is not a thread asking if it's ok to use regular gas in the revup motor found in the 05 G35 6mt sedan. The topic has been beaten to death and we all know it is not recommended. Anyways, we picked up an 05 6mt sedan over the weekend and found out that the previous owner used regular gas in the car for all it's life for 80k miles. What are some immediate things to do to correct and "lessen" the damage (if any) done to the motor already? Going forward, we are obviously going to use premium.

 

How did you "find out" they used 87 the whole time?

 

About all you can do is use premium from now on.
Maybe change spark plugs too, any knocking can cause spark plug damage.

I doubt it would have done any engine damage, as soon as the ECU detected the slightest engine knock, it would have retarted the timing and richened the fuel mix to prevent damage. Under most normal driving conditions, it probably wouldn't knock on regular fuel anyway.

 

You might need to worry about the cats from rich fuel. Also, since it is rev up, you might need to worry about the oil consumption issue.

 

Regular gas will cause no harm in most modern vehicles as the ECU will almost immediately detect detonation and retard the timing accordingly.

However, with retarded timing, performance will suffer compared to using fuel that allows a combustion cycle closer to top dead center.

I wouldn't worry if I were you.

Lower octane fuel also burns more cleanly at lower temps, so you are less likely to have alot of built up carbon deposits if the previous owner used lower octane fuel (high octane fuels contain alot more detergents for this reason).

 

id just blame anything that happens on the car in the future on the 87 octane then shrug your shoulders and repair it at that time. Just follow the standard maintenance. There's no mitigation necessary or possible that I know of