I have a 2013 S60 T5 AWD. The owner's manual says 91 for top performance. Now with gas prices being what they are, and things for me being tight, I was thinking of switching to 89 octane. I won't go down to 87 that's for sure. But I'm wondering, what kind of performance loss will I notice using 89 octane instead of 91?

Thoughts?

 

first concern is what's best for your car. Look at your owners manual and see if it says 91 is recommended or required. As to performance loss, what happens is the knock sensors will detect any pinging (aka pinking) and the ECU will retard the spark (not sure if it also richens the mixture) so you will get slightly less power on WOT. If you drive with a soft foot, you probably won't notice the difference. If 91 is required then running less than the recommended risks misfires etc so again if you drive agressively you may risk misfires and engine damage. If you drive with a soft foot you probably won't notice much difference short of a possible check engine light. That said, the way to go is to follow the owners manual recommendation. If you really want to save a few cents a gallon, next fill up put in half a tank of 93 and half a tank of 89 to make your 91 (since not all brands sell a 91). If you check the prices, that will add up to less than what other stations charge for 91.

 

I don't dare to do that with a turbo.