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

[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?

[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

[Tony_Whenua]

Sweet, thank you

Car has been going fine so far

[DATSN1200]

In the Datsun use the higher octane fuel
I got 44 miles per gallon from Wellington and return to the Taupo event recently
Use BP or Shell
Keep away from Mobil or Caltex because of the additives

[classicdat]

1200s were tuned to run on 89 I think back in the day, just give it a boot full, in a higher gear, at low speed, if it sounds like a bag of marbles back off, (retard, lol) your timing again and try again, as long as it is not rattling all the time you should be fine, although you can not always hear detonation. As Dan said, unless it is tuned for it a Higher Octane will not pay you any dividends. Advancing the timing was heading in the right direction.

[Feldstein]

Good to know that there are signs to pay attention to without doing permanent damage. I thought switching to a fuel like that is a big no-no.