Hey, first time poster.

 

I just got a '98 Legacy Outback. Unfortunately, the Owner's Manual did not come with the car. I've been trying to find if I need to use a gasoline with more than standard, 87 octane gasoline. I know with some higher compression engines it is necessary and I don't what to do unnecessary damage to my car if I can help it.

 

Any help is much, much appreciated.

 

PS - I love the car so far! It's great!

regular or high octance or mid octane will do, but off course a higher octane is always better.

but off course a higher octane is always better.

 

Why do you say that?

[...]I just got a '98 Legacy Outback. Unfortunately, the Owner's Manual did not come with the car. I've been trying to find if I need to use a gasoline with more than standard, 87 octane gasoline. I know with some higher compression engines it is necessary and I don't what to do unnecessary damage to my car if I can help it.

Welcome. Subaru says the '98 OB will run on 87 octane, and the engine controls include a knock sensor that will retard the timing a bit if needed. Some people claim that they get somewhat better performance and/or gas mileage with the next higher grade. I'd suggest that you run a few tankfuls of 87 and calculate the mpg. If you're satisfied with performance and mileage, continue with the 87; if not, move up a grade, run through a few more tanks, and see if the mileage or performance improve (I suspect they won't, or if they do won't be worth the additional expense).

 

Contrary to what some may say, higher grades of gas provide little or no advantage if an engine doesn't require the higher octane.

Why do you say that?

Good question.

A year or so ago I ran a test on my Forester running higher octane. I got no change in fuel mileage at all.

Why do you say that?

His car may need higher octane! He as high mileage some carbon buildup on combustion c. thus the need for higher octane

His car may need higher octane! He as high mileage some carbon buildup on combustion c. thus the need for higher octane

 

That may well be true, vic/se. But my red flags go up when someone makes a blanket statement that is flat out wrong.

 

Higher octane gas is most certainly NOT "always better!"

Higher octane does not ever mean beter just... More expensive at times... Turbocharged definatly to be on the safe side but non turbo with a 2.5 naa unleaded will do. you dont really need to worry about detonation with one of those although.. is has happoned before but in very rare scenarios