What Fuel to use ??

[CroDude]

Hi there everyone
I recently both a used subaru STi
I live int he Greater Toronto Area and just wanted to known what do you guys that live in the area put in the car. I was told either sunoco 94 or shell v-power work well.
What i understand is that sunoco has ethanol in there gas and that makes fuel mileage worse, and that shell v-power has no ethanol.
What is the better option i want this car to last for a long time i don't mind spending more on the gas, just which one is actual better.

Thank you for all the help

[Anub1s]

Welcome!

Always use premium, whatever is the highest rating (at least 91, 93+ AKI is preferable and advised by Subaru to be used in STis). As for ethanol or non ethanol, it's your choice. Ethanol is known to eat away at certain rubber components, but modern cars are fine to run E10 fuel. I think it's pretty much standard in the US now, BTW.

There are known fuel mileage decreases when using E10 over "pure" gasoline, so it's up to you on what you'd like to run. Just maintain the recommended octane rating and you'll be right as rain .

[MainFrame]

Use "Premium" fuel..

[anxiouz]

Use the highest non-ethanol octane you can get at the pump. So it sounds like Shell is your best option.

Anything with Ethanol in it will get less MPG but likely more HP. If you're tuned for it you may want go the route. If the Sunco-94 with E is all over the place I would honestly recommend a pro-tune to run that stuff. I don't have any experience with E in Subarus but in my Evo 8 all I needed was an upgraded fuel pump (Walbro 355lph) and larger fuel injectors (1,000cc) to run it and I was at 370whp with just a turbo-back exhaust. But I had a dual map so I could switch to 91 octane real easy since E85 is so inconvenient to get here.

Long story short...run the highest non-enthanol octane you can. OR get tuned to run the stuff with ethanol in it. You'll burn more but make more power. In my Evo the price difference between E85 and 91 octane (the best we can get here in CA) was like $0.70 per gallon so it was actually cheaper to run E85 and I made 70-80 more whp at the same boost level. That's magic sauce as far as I'm concerned.

[SeattleJeremy]

Always use premium, whatever is the highest rating (at least 91, 93+ AKI is preferable and advised by Subaru to be used in STis).

This.

[zax]

Use the highest non-ethanol octane you can get at the pump. So it sounds like Shell is your best option.

Anything with Ethanol in it will get less MPG but likely more HP. If you're tuned for it you may want go the route.

I hate to break this to you, but all modern fuel contains ethanol, even if it isn't advertised as "10% ethanol." In fact, I think it's mandated.

Sent from my Droid using the "I don't give a ****" app

[Anub1s]

Use the highest non-ethanol octane you can get at the pump. So it sounds like Shell is your best option.

Anything with Ethanol in it will get less MPG but likely more HP. If you're tuned for it you may want go the route. If the Sunco-94 with E is all over the place I would honestly recommend a pro-tune to run that stuff. I don't have any experience with E in Subarus but in my Evo 8 all I needed was an upgraded fuel pump (Walbro 355lph) and larger fuel injectors (1,000cc) to run it and I was at 370whp with just a turbo-back exhaust. But I had a dual map so I could switch to 91 octane real easy since E85 is so inconvenient to get here.

Long story short...run the highest non-enthanol octane you can. OR get tuned to run the stuff with ethanol in it. You'll burn more but make more power. In my Evo the price difference between E85 and 91 octane (the best we can get here in CA) was like $0.70 per gallon so it was actually cheaper to run E85 and I made 70-80 more whp at the same boost level. That's magic sauce as far as I'm concerned.

He's talking E10, not E85. E85 is a LOT different than E10. E10 is basically gasoline with a bit of ethanol in it (10% ethanol), E85 is basically ethanol with a bit of gasoline (or other hydrocarbon) in it (85% ethanol). E85 is MUCH higher octane than E10 is, which is why you gain so much power with it, and also why you get worse gas mileage, and why you need to tune for it, and run bigger injectors, new fuel lines, and fuel pump.

E10 doesn't need to be tuned for per se, unless limits are being pushed and you're switching from one type to the other, then datalogging is suggested of course.

[anxiouz]

Ah, gotcha. We have like no options here. Thanks for the correction and info.

[Anub1s]

Ah, gotcha. We have like no options here. Thanks for the correction and info.

No problem. E10 is actually mandated in certain areas, but not ALL of the U.S. It's used mainly to reduce emissions, so it's very likely that you being in CA, have E10 based gasoline at the pumps by now, though I don't think it's actually mandated there yet. Go figure that it's also common in the midwest since it's corn based fuel.

Most of the fuel here in Utah is E10, BTW. I have no problem using it, my car actually seems happier with it.

[anxiouz]

Cool. All I know is that when I recently flew out to MN to see a newborn nephew...my first comment was not about the baby but rather a "nice...you guys have 93 octane here. Sweet!".

The 91 octane in CA is absolutely terrible. At best you're getting what is advertised. But the norm is shizzle so resorting to E85 or meth or something else to help is probably more common here than elsewhere. I would probably rate our 91 as closer to 87. Even at the same station you can see a clear variance tank to tank. It's frustrating as hell but the 76 stations seem to have the best or most consistent octane levels.

[Anub1s]

I've heard that about CA's 91 octane. Cobb even has a specific map for CA/AZ/NV 91 octane...

I also hear you about the 93 octane. It's the best part about SCCA events in Idaho, I get to use 93 octane

[CroDude]

Thanks alot guys from the look of things i should be using the sunoco 94 in STi

[MainFrame]

Sunoco 94 would be a good bet, Shell 93 octane would be fine too. E10 can actually help keep your fuel system clean, and it's not going to decrease your mileage.