89 and GT Performance

[lsimy]

I've seen this discussed before but still curious: This weekend I drove to my folks a few hours away and decided to fill up with 89 (2003 GT) at Shell. What confused me was that I got excellent mileage and the performance seemed to be almost comprable to 93.

Am I nuts or is this possible? If it might be safe to run 89 (not cheapy gas stations either), I'd like to continue. The fuel door just says, "recommended" not "required".

Any ideas? Thanks very much !!

[QuicksilverDon]

I'm not an expert, but I think if you run another tank of 89 in warmer weather or up steep hills, you may notice a difference. You had some 93 in the tank, so your mix was over 89. There's a knock sensor, so you should not hear pinging, it backs off on spark timing so you lose some power. I'll bet you could alternate filling up with 93 & 89.

[MINIMOTOMike]

Originally Posted by QuicksilverDon

I'll bet you could alternate filling up with 93 & 89.

thats what i do with no ill effect

[taupe02]

I may be wrong and I'm sure the technology has changed over time, but an older vehicle I had (1989 Dodge Daytona Shelby) had the same basic intercooled turbo as the GT does and from what I was told, the higher octane gas burns cleaner and over the long run, is better for the turbocharger. The turbocharger is basically a fan that forces more air into the intake and using the lower octane "dirtier" gas, down the road could cause the turbo to "gum up" and begin to have problems. All I can say is the car is still in the family and the odometer quit about 1 year ago at 260,000 miles and it still has the original engine, turbo charger, and everything else with no problems, but I always filled up with the highest octane available. Like I said, I was just told all of this so it might be totally wrong, but I went ahead and followed the advice and now almost 300,000 miles later, something worked!!!

[RallyDRock]

Originally Posted by MINIMOTOMike

thats what i do with no ill effect

but this is for turbo gt
if you run anything higher than 87 in a N/A PT you are wasting your money

[airbillster]

But if you have the Turbo, Taupe02 is right on the money, it's the long term effects that are devastating.
"The turbocharger is basically a fan that forces more air into the intake and using the lower octane "dirtier" gas, down the road could cause the turbo to "gum up" and begin to have problems."

[lsimy]

Cool. I'll stick with the 91/93 octane. Most premiums are 93 here in Virginia. Thank you for the replies !!!! I'll only use 89 in a pinch or on intended long trips !!!!

Airbillster, cool to see you are from Gainesville. I drive through Gainesville and Warr. on the way to the folks place.

[JOEM]

Originally Posted by taupe02

I may be wrong and I'm sure the technology has changed over time, but an older vehicle I had (1989 Dodge Daytona Shelby) had the same basic intercooled turbo as the GT does and from what I was told, the higher octane gas burns cleaner and over the long run, is better for the turbocharger. The turbocharger is basically a fan that forces more air into the intake and using the lower octane "dirtier" gas, down the road could cause the turbo to "gum up" and begin to have problems. All I can say is the car is still in the family and the odometer quit about 1 year ago at 260,000 miles and it still has the original engine, turbo charger, and everything else with no problems, but I always filled up with the highest octane available. Like I said, I was just told all of this so it might be totally wrong, but I went ahead and followed the advice and now almost 300,000 miles later, something worked!!!

I had an '88 Daytona Shelby Z and the premium gas was recommended to avoid detonation--a very good reason to spend the extra money for premium gas when you have a high-output turbo.