2015 yukon denali gas?

[ecanem]

If I use 89 would it really be that bad?

If GM is recommending you use 91 then the compression ratio likely calls for that level of octane. You can use 89 and your ECU will compensate by retarding timing and running a richer mixture. In the short term, it will reduce fuel economy, in the long term, clogged injectors and other issues could occur.

 

[fireboat]

In my Denali, I use 91 octane, I figure even with the higher cost, it is offset by the slight increase in gas mileage because the ignition timing is not retarded. I think I get about 1-2 more mpg with the premium.
Plus, there is a slight improvement in performance though it is not that noticeable.

 

[Jproy]

If GM is recommending you use 91 then the compression ratio likely calls for that level of octane. You can use 89 and your ECU will compensate by retarding timing and running a richer mixture. In the short term, it will reduce fuel economy, in the long term, clogged injectors and other issues could occur.

What he said.

 

[JackJare9455]

Just use what the book or dealer tells you too! Don't short your 60k+ (maybe more) investment for a few dollars a tank! Jeez