How does your GT run on regular gas?

[PoCoBob]

A couple weeks ago I did an out of town trip that took me through several mountain passes. Since I knew I was going to burn a tank of gas off just cruising on the highway I decided I'd use 87 and save some money. The only time I've used 87 prior to this was when the car was brand new and during break in. That will be the last time I use 87, the engine knocked like crazy at low rpm's so I had to keep it in sport mode so the rpm's stayed a little higher. Even then I still had knocking. It wasn't until I filled up twice with 91 that things went back to normal, both times I was at 1/2 tank when I topped it off trying to get higher octane in there. Mine's a gen 3 engine which has higher compression than the previous versions so others may have better luck but I'll find other things to save money on and stick to 91.

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[Cory S]

A couple weeks ago I did an out of town trip that took me through several mountain passes. Since I knew I was going to burn a tank of gas off just cruising on the highway I decided I'd use 87 and save some money. The only time I've used 87 prior to this was when the car was brand new and during break in. That will be the last time I use 87, the engine knocked like crazy at low rpm's so I had to keep it in sport mode so the rpm's stayed a little higher. Even then I still had knocking. It wasn't until I filled up twice with 91 that things went back to normal, both times I was at 1/2 tank when I topped it off trying to get higher octane in there. Mine's a gen 3 engine witch has higher compression than the previous versions so others may have better luck but I'll find other things to save money on and stick to 91.

Your PCM would be pulling spark advance far faster than you could audibly hear it........

 

[PoCoBob]

Your PCM would be pulling spark advance far faster than you could audibly hear it........

So if the PCM is quicker than your ear why would this even be in the owners manual?

Note that it says the recommended octane is 91 and as soon as I got enough 91 back in the tank all the knocking stopped. It's too much of a coincidence to assume the two aren't related.

 

[Cory S]

So if the PCM is quicker than your ear why would this even be in the owners manual?

Note that it says the recommended octane is 91 and as soon as I got enough 91 back in the tank all the knocking stopped. It's too much of a coincidence to assume the two aren't related.

I don't know. It's probably the same thing they have printed for 40 years.

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