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Free 91 fuel ... but is it worth it?

Posted: Sun Jul 01, 2018 12:37 pm
by Tony_Whenua
The Mrs gets free fuel from work now but it’s 91 unleaded. Car recommends 95 and some websites are saying yeah and na to using a lower grade.

Any concerns with using 91 in a 2007 Subaru Impreza?

Also read it’s a waste of money running 95 in a car tuned for 91. What were the A12s tunes for? I’ve got my car on 98 but timing is slightly advanced...That’s legit right?

Re: Free 91 fuel ... but is it worth it?

Posted: Sat Jul 28, 2018 10:52 pm
by datsunboy
Give it a try and see.
If you're not flat footing it around town it'll be fine.
Petrol has a certain amount of energy per liter.
There is no difference between 91 and 95/98 in terms of energy so won't make any more horsepower.
All it does is raise its resistance to detonation.
So running higher octane fuel allows you to run more timing which in turn makes more power.

There is no benefit to running higher octane fuel in a car unless you tune it to take advantage of it.

If the car is tuned for 98, you can run 91 just fine if you're not pushing the engine and just cruising.
Just be careful and listen to the engine.

Sent from my SM-G930F using Tapatalk

Re: Free 91 fuel ... but is it worth it?

Posted: Sun Jul 29, 2018 6:08 pm
by Tony_Whenua
Sweet, thank you

Car has been going fine so far :thumbsup: