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There a lot of talk on this topic, mostly quoting of numbers out of manuals. I am looking at a 2010 forester, trying to make up my mind between the turbo and non-turbo. Has anyone run one (with turbo) with super for an extended period of time?? I would like to get some first hand info... Thanks much

only safe way is to retune with methanol....the performance will not be the same as running premium but once retuned it would be a bit close to it.....

But what will super do?? Besides loss of power, will it cause cause knocking and/or pinging?

That's why it needs to be retuned so that it would limit detonation and cause no damages to the engine.
I personally don't see why you would wAnt a boosted car and suffer the performance by running super but everyone know where they can reach

My advice is if you are concerned about fuel, purchase the Na model because later down the road you would want to open her up

Most wrx/sti (especially JDM) are tuned for 97RON. Locally, our premium is 95RON and super 92RON. You can already see the huge difference between the factory tuned recommendation and local super. Even premium on an untuned JDM platform is not advised.

Any sort of tune with super as the base fuel will probably result in a performance cut.

Thanks for the info guys, I am just doing some research before I make the buy. I have no plan of putting out for premium.. If i get a little power loss, I can live with that, but I dont want to go messing with re-tuning and methanol and all that..and more so I dont want to end up in a situation where I damage the engine!! I have gotten so many conflicting reports.. I think i'll play it safe and go non-turbo... Thanks much for the info..

If you don't plan to do a retune then definitely do non turbo.

The Subaru ECU is very smart and self adjusting and it will retard timing if it detects knock. If the knock is bad enough it will push itself into safe mode and run wastegate boost as well.

In any event, the potential knock that may occur from running super can be bad enough to over time damage your engine. A tank of bad gas can do it even sooner.

Running super puts you right on the threshold for dangerous knock. You may be lucky or you may not. This is probably why the feedback as been conflicting.

Super and octane boost?

If u want to use Super buy a non-turbo! Do not use super with octane boost and think it is anyway close to running premium. The ECU can only accommodate for so much knock reduction due to low octane gas.

What about mixing super and premium? 50/50.

93.5 RON would work?

Hope dem gas stations not doing that already! LOL

I have a 2010 forester xt and have been running super without a tune for almost a year without issues.

Pull a learning view. Check the IAM and the fine learning knock correction (FLKC). It might tell a different story.

there are STi-s that run super with meth kit - savings used to upgrade parts - a good tuner should be able to help

16 cycles wrote:there are STi-s that run super with meth kit - savings used to upgrade parts - a good tuner should be able to help

I know a few legacy owners that have done the same.

The guy said he doesn't wanna go thru that hassle of mixing meth etc

DVSTT wrote:What about mixing super and premium? 50/50.

93.5 RON would work?

Chemistry wasn't your strong point in uwi was it?

tr1ad wrote:

DVSTT wrote:What about mixing super and premium? 50/50.

93.5 RON would work?

Chemistry wasn't your strong point in uwi was it?

Me ent know how I have distinctions in that for CSEC and CAPE nuh....

And yuh still chupid so?

tr1ad wrote:And yuh still chupid so?

Well educate me, what's wrong with my logic? I'm not doing petroleum engineering.

Man add rons and divide by two lol haha

Aaron 2NR wrote:Man add rons and divide by two lol haha

Still waiting on an explanation since you obviously know better.

But Ent you have chemistry distinction ?

You should be able to tell us that the lower grade mixture can override the faster combustible higher grade

Quit while you ahead and try to offer meaningful advice.

Have you ever owned a subaru? Do you understand the impact a RON lower than what is recommended can do?
Are you even aware that all these "octane boosters" and treatments can do more harm?

You have the Chem background.... You tell us

I have always been a firm believer if you cannot properly maintain a vehicle then it isn't for you. Especially if you're concerned about fuel Atm then if something mechanical goes wrong then what's the next corner cut. If you can afford a na then go all ahead with the purchase

I got rid of all dem fass up car due to my long distance runs, it wasn't economical and I switched to diesel. Recommended rating is exactly what it is, recommended if you have the cash do an Ecutek tune.
Other than that, no sense in having a nice car but worried about fuel costs

^^Like you have shares in Tradewinds or wah lol

Talked to a leggy owner today and he says he runs super in it with no issues.
Me, won't take that chance. Would run super with a retune for water meth.

As Lance says.... Log and I'm sure the difference will be seen

Normally it's mixed 50/50 with water and applied via inter cooler spray.
Last time I used it was 40 for 8 gallons IIRC

aem make a na kit that utilise your maf to engage, i do not know anyone personally who has it installed.


there are a number of sellers of methanol locally...tuner imports is one but he retail VP meth and not the locally produced methanol. $40/gal

i tried the industrial grade a couple times, but the last batch i got had moisture in it and threw my entire afr off. ended up having to drain the methanol tank and buying more methanol.