Fuel recommendation for 2014 Forester

My 2015 pings on 87 octane so we run 89 octane gas.

Hmmm...shouldn't. Try other pumps? Maybe there's crap or water in your source?

I had the ECU update for high altitude pinging which helped a bit but not enough. I asked my dealer if there are any more update and they said no. High altitudes are murder and we need premium when crossing the Sierra's. Octane booster also helps but for ordinary driving 89 octane is good enough. It pings regardless of the fuel source.

An old trick I learned when piloting G37xs was that because of the non-linearity of octane distillations and price strata, if you combine equal amounts of 93 and 87 octane you get a 91 octane for the same price as 89 mid-price at the pump. Easy way to achieve this is just to alternate fill-ups of 93 and 87 when around the 3/8-1/2 tank level. Works well, and maybe you'll be ok with this "ersatz" cheap 91. It may be a PITA to try to remember which to put in if you forget the preceding fill-up unless you create a little mnemonic device like the common day of the wee you gas up, or maybe a visual marker in the car that you flip...or maybe use the A and B trip odos alternately? Have fun. Ern

I have done that before. Not too many people know how fuel octane averages.

Not sure I'd do it on some high-pressure turbos nor my Cosworth boosted Miata, where dicking around with "fake" 91 isn't as safe as just ponying up for 93 and no worries. Keep warm. Ern