What fuel to run in 89 GT?

[Jekyl]

I was wondering what grade of fuel I should run in a stock 89 GT...??? The only mods are full exhaust o/r H and K&N CAI.

 

[91notch5.0]

87 is fine. it is all i run

 

[89MustangGX]

Whatever the lowest grade you can user without pinging.

If 87 runs fine for you, run nothing more.

 

[HISSIN50]

i prefer gasoline. i tried diesel - it did not run too well. i tried propane - it would not run at all.
but it seemed like gasoline worked pretty well.

i agree with Adam.

 

[Shakerhood]

It depends where you set your timing!

 

[87gtconv]

I agree with Shakerhood. My vert is set at 14* and in the summer I have to use 91 octane but if I run it at 10* it will run all day on 87. Of course it will run slowly!!

 

[Camman]

I agree with Shakerhood. My vert is set at 14* and in the summer I have to use 91 octane but if I run it at 10* it will run all day on 87. Of course it will run slowly!!

interesting theory. The lowest octane fuel you can run w/out detonation will give you the best hp/mpg. For conversation sake my bone stock 89 made 202/287 hp torque with 92 and 211/298 tq with 87, car was never dismounted from the dyno, runs were made back to back 3 each. I did this and won about 500 bux for my auto class Thats not as good as betting n00bs that your wheels will turn different ways in the back if it is jacked off the ground. I must have made a killing over the years with this one, of course now that I mainly drive the 89 I cant pull that one anymroe. :OT:

 

[HISSIN50]

interesting theory. The lowest octane fuel you can run w/out detonation will give you the best hp/mpg.

quoted for accuracy!

if one has to run higher octane fuel to interact with a timing bump, it is a waste (more spark advance + less volatile fuel = wash). there is also a point of diminishing returns - one can run more timing but not see detonation, yet lose power. the advent of dynos was great.