Audi A5 Forum & Audi S5 Forum banner
1 - 5 of 5 Posts

·
Registered
Joined
·
10 Posts
Discussion Starter · #1 ·
I recently got an 2011 Audi A5 2.0t, and I know the car recommends 91 octane but my local gas stations only have 87, 89, and 93. I know I can run 93 and be fine, but it’s pretty expensive. Could I run 89 octane without any knocking/performance issues?
 

·
Administrator
Joined
·
473 Posts
I wouldn’t risk it. Maybe you can mix half a tank of 93 with half a tank of 89 and get 91? Just an idea, please research that before you try it. 😎
 

·
Registered
Joined
·
538 Posts
The car is tuned to run at 91 minimum octane. So if you don't have 91, then go with 93.

My understanding is that when you use a lower octane, the computer can probably compensate by adjusting the timing. However, you'll lose out on power and mpg. Also, you run the risk of having other issues (e.g. carbon buildup/hot spots) that causes so much pre-detonation to the point where the computer can't retard the timing enough.

I haven't seen any real long-term studies done. Anecdotally, I've never heard of anyone saying their engine failed because of lower octane.
 

·
Premium Member
Joined
·
3,437 Posts
Go for 93 mate for peace of mind plus engine care. Also I use some STP or similar every few tanks just to try and keep the injection system clean. 91 is ok from time to time but best mixed with 93.
 

·
Registered
Joined
·
171 Posts
Go for the 93 octane. Just drive very economical and never be tempted to put your foot down.
 
1 - 5 of 5 Posts
Top