On our way home the other night I stopped to fill up the '11 Outback. Any time I fill that thing up I have to triple check to make sure I'm putting the right fuel in, considering there are 4 different types, and how am I supposed to know that it was hung up on the correct spot... Anyways, after filling up I mentioned to my wife all of that and how I'm just too used to filling up on 91. She then posed the question of what is E88 and why can't we just use that. It has a MY range and our car fits into that... Well, the little I know if 88 is that it's less efficient, even that I'm not really sure of. So then I got thinking about fuel. Why did they start making 88? What's it good for? What about 91? My WRX has a OTS map tune for 93 but I've just been running 91. Am I killing my engine doing that? Then I thought, I gotta research this and figure it out. Eh, no time for that right now. Oh hey, MNSubaru and the knowledge bank found there!
Not sure if that's killing your engine, but I wouldn't run anything lower than what the tune is for. You can go the other way however. Tune for 91, run 93.
88 Octane (E15) is a blend of 85 octane and 15% ethanol which bumps the total octane up to 88. It is okay to use in flex fuel vehicles such as my 2011 Suburban. It tends to be about $.25 cheaper than 87 octane E10 offered here in Rochester. I would not use it if you are not tuned for it. It is not a high performance fuel and you will have predetonation and possibly destroy your engine. I think my wife put some 88 octane E15 into her pontiac vibe and got a P0171 code- too lean. You need bigger injectors or a fuel system that can adjust on the fly to be able to use it in a non-boosted car. In addition, if you are not tuned for 91 non oxy (i.e. 0% ethanol). I wouldn't use that either, switch maps to 91 octane, retune for 92 if you can find it or find 93. Don't put lower octane fuel into your car than you are tuned for. On another not so unrelated topic, E85 (85% ethanol, seasonally 51 to 70%) is a mix of 85 octane and 85% ethanol which can bump the octane up to theoretically 105, but in practice more like 100. You should not use this unless tuned for it and have the necessary supporting mods (fuel pump and injectors)
My sister-in-law's '08 Impreza was just in the shop chasing a mysterious misfire. Plugs, wires, coil....no change. Master tech asked her if she had filled up with E15 at Kwik Trip, and she said yes. Pumped it out and refilled with regular fuel, and it's run great ever since.... Even if it runs as-intended on it, your mileage will be reduced enough to negate anything saved. Stick with plain old fuel.
Shoot, very nice info, thanks. Makes sense. Unfortunately I haven't found a gas station that has 93 in Duluth. Haven't looked super hard but I'm by the mall area and have checked most of them over here. Could be the reason my car doesn't seem too happy on occasion. I knew that 88 octane was for flex fuel cars, just totally slipped my mind. I'll need to figure out my AP or something because it's definitely not tuned right. The map is for stock air intake and it definitely doesn't have that.
I feel like the BP that we always went to on the Duluth Cruise had 93? That’s where Chet snapped the gas hose in half by driving away with the nozzle.
Here ya go https://find93.com/ 88 isn't limited to flex fuel... It is suppose to be a small enough difference in eth content where any car with a modern knock and o2 sensor can figure out fuel trims. Subaru in my experience swings it's trims around too much (even on pump) for it to work efficiently. Why this is, I don't know but a flex sensor narrows the swing down a lot.. Flex in a wrx for milage/savings/compatability, is pretty niche. A tuner can make an 88 map with stock injectors if you had your heart set on it. I'd just stick to prem if you don't do the flex fuel sensor. Too much effort in swapping maps back and forth. Also, BP in Apple Valley is only 91 but the shell on cedar is 93. IIRC, BP and/or shell is a franchise and the octane availability is dependent on the franchise owner.
That's right down the road from me, swung in there yesterday to use their air and I'm pretty sure, from a distance, that it said 91. Will have to double check. Thanks. No, I'm not planning on using anything but reg in the 11 OB and prem in the WRX. My wife was just wondering what 88 was and why not use it.
I believe the AP's come with an over the shelf tune for both 91 and 93. Check to see if your AP has both. Otherwise, I'm sure someone here has a stock Cobb tune for your MY WRX and might be able to send you the file.
Yeah, no dice on the 93 at that BP anymore. I'll have to check on that. It's a V2 AP, so no more support, and I was having trouble setting up the software on my PC and getting it to recognize the AP. Can you just remove the current map and it'll go back to stock?
Yes when you "marry" the ap and ecu, the ap backs up the original ecu map. Divorce is basically recovering the ecu to its backup. However, you might want to try marring it again to see if the 91 map is there. If I recall correctly, the ots maps are baked into the firmware and will come back when you reset the ap.
Found out that the new fleet farm they put in up here sells 92. I'd assume this would be better to run than the 91 but still not up to par?
