Just picked up a GT & was wondering why the manual calls for 87? All the V8's I have owned all required 91 or higher. WIll it hurt anything if I deviate from the owners manual & run 93? Is there any noticeable power difference between the two? Not too concerned about the MPG's but is that affected as well? Thanks.

 

It would be a total waste of money running higher then 87. Unless you tune for it and go higher then you will see a performance improvement.

 

Yep. Unless you run an aftermarket tune, the stock programming although the PCM will adjust won't have a noticable difference. Run a programmer with a 93 tune and the difference from stock will be amazing.

 

+1 to both of the above posts.

 

A lot of people can't use 87 though as the car will ping. Mine does so I have to run the next step up in octane. This happens even with my tunes. But I noticed the pinging only happens when the engine is cold, once it's warm I don't think it does it any more. I would love to find out why some of these cars do this.

 

Get a tune.

 

Only run what the manufacturer recommends, in this case 87. Octane's not quality but rather the volitility-rate at which it burns. But as the others have said, get a tune then run 93 w/more power!!!

 

the only car that would run more hp with higher octane is the new bullit mustang, because it's tuned to detect the higher octane and change the timing.

 

also guys we should mention running a higher octane without a tune will cause more carbon buildup quicker so then you can have some fun with the TSB on removing the plugs!!!

 

I put 87 all the time, i would recommend a good gas station because ive heard plenty of storys of stations using cheap 87. Gotta use the big guys who are profiting a couple billion a year