Originally Posted By: Vikas
Unless the car says "under penalty of death, do not use anything less than premium" in the owner's manual, I routinely put regular gas in in. All my cars are 200K+
Back in the day before modern computer controlled engines that would be a good way to burn a piston. With the event of EFI and knock sensors you can get away with it.
If a high compression engine requires 91 say and you fuel with 87 it just retards timing until pre ignition stops. Most modern cars have multiple programs in the ECU for just that.
On the flip side you won't get all the advertised HP or mileage, sometimes this is noticeable sometimes its not. Depends on the set up and how much timing has to be retarded.
Something like my uncles custom race motor will barely run on 93 and since its carbed it will just ping and be all sorts of un happy. He typically runs 108-113 octane. Now his wife's Acura doesn't care if its 93 or 87. Computers are wonderful.