I bought an 03 Forester and I am new to this site. It looks great and I am sure that I'll find it useful. Just one question. What USA octane rating does everyone recommend I use in my Forester? I was running 87 but the engine knocked. Now I am using 89 and everything seems okay. The manual says 87 or higher, but I had problems with 87. Any suggestions would be helpful. Thanks

I ran 87 when I first got my Legacy, never knocked or pinged. Feeling cheap, I ran 93 for about 2 years, thinking I was doing my car a favor. Upon Legacy777's suggestion, I switched to 89 octane. My Legacy has never run better than on 89 octane gas. As a result, I put 89 in my XT. So I guess that's 4 examples (including yours) that normally-aspirated Subarus seem to run best on 89 octane gas...

If you want to keep using the 87, you might try resetting the ECU with 87 in it. I've never done that, but from my understanding of how the ECU calibrates the engine, it might work (keep it from knocking).

Wow...thanks for the help. I have never owned a subaru before and I didn't expect to hear an engine knock going up a hill with 87 octane in the tank. Since the car was new, I, of course, freaked. The owner's manual said that it runs on 87 or higher, so I couldn't understand why I heard the knock. I've switched to 89 and have had no problems, but I am wondering why I heard the knock with 87 octane and if there are underlying problems with the engine that may explain the problem. I have been told that with a knock sensor, I shouldn't hear any knocks. What does the board think I should do? Thanks for the help. I've really learned a lot.