Join Date: Apr 2008
Location: Saint Louis, Missouri
Car Year: 2006
Car Model: Forester XT Limited
Transmission: 5 Speed Manual
There is a lot of posts already on here if you search for "recommended fuel for turbo" or something like that. This seems to always be creeping back in. LOL
Well, just to sum it up, if you have a Subaru with a turbo, it is critical that you use nothing less than 91 octane. If you run for extended periods of time on regular, you will eventually burn up your turbo for starters, which wouldn't be covered under warranty. I don't know why your dealer told you it was just fine to run regular if premium is recommended. Obviously he didn't get the memo! LOL
If you look in your manual, it also says that in an emergency, you can use the regular gas if premium cannot be found. If you do use regular gas, you will be taking a severe hit on performance (and not just HP will be affected!!!) as the knock sensors will pick up on this and have the ECM (Engine Control Module) to adjust the timing to accommodate the lesser fuel.
If your car specifies regular 87 octane, than it will not run any better or get better gas mileage and you will be wasting your money; It will only run hotter. The ECM cannot adjust for this scenario as it was only tuned to run on the regular 87 gas. I have seen some stations in New Mexico, Arizona, and Nevada that sell regular 85 octane and mid grade 87. Just make sure that you are always using the fuel the car manufacture recommends.
EDIT: Octane Boost WILL NOT improve the quality of fuel. It is not a magic wand to fix everything. As an additional not to that, for the cost of premium fuel vs. regular fuel in the tank, the cost to put in the premium would be cheeper than buying the bottle of boost to put in after the fact!
'06 XT w/ 5MT
Last edited by INSubbie; 05-12-2008 at 04:40 AM.