Hi Scotty!
I have a 2020 Subaru WRX with the 2.0L DOHC Boxer Turbo 4cyl and a 6-speed manual. The engine has a compression ratio of 10.6:1, and there are roughly 7900 miles on the car. I have question about which octane fuel I should use with the car. Subaru recommends, but does not require, 91 AKI fuel. Since Shell does not sell 91 AKI, I put in V-Power 93 when I first got the car. However, since I noticed that whenever I pushed the car while running 93 a bad smell soon followed, and the fact that fuel prices have gone up, I stopped using 93, and went down to 89. Anyway, my question is, will using 89 cause damage to the engine? My dad has always gotten fuel at Shell, and so do I, but I know the local Sunoco station near me sells 91. Should I put 91 in from a different station, or stick with 89 from Shell? My dad considers Sunoco "bad gas," so that's another reason to stick with the 89 at Shell...
Thanks, and let me know what you think!
Your owner's manual will tell you what octane rated fuel to put in the car. It will most likely run fine on 89 or 87. You probably won't be able to race around like WRX guys do because you'll lose some power. Regular and Midgrade don't take high compression like premium very well, and will cause the engine to compensate for pre-ignition. Your owner's manual is the first place to look for this information.
Gas in the U.S. is pretty much gas. Cheapo brands like UDF, etc. aren't Top Tier fuel like Shell, but they have the federal minimum standard for fuel detergents. Sunoco is Top Tier as well. Nobody sells "bad gas" unless they get a bad batch, etc. I usually only buy Shell gas myself, but V-Power makes you pay for their advertising. That's why it's $0.20 higher than most other places' Premium.
Thanks for info Justin!
I basically agree with Justin. Your car can mostly compensate.
That said, 87 might be pushing it. At that octane, you’ll end up doing more of your driving at higher boost, which will increase chances for preignition (if only slightly) and eat up what cost savings you would have had.
FWIW, I have an ‘18 WRX and have never used less than 91 octane.
Thanks for the input! Appreciate it!