should i be putting premium in my car (85 TPI 5.0)?

 

I always try to run premium,simply because I get a heck of a lot better gas milage.

 

It depends on what the owner's manual calls for. Now, if you change from stock then you have to go with 93 octane if you are running high compression.

 

its all stock

 

The original Camaro Owners manual recommended 92+octane when the cars were new. Just depends what you want to run in your car.

 

If it isn't pinging it will make the same (or more) power with the lower octane. The octane rating is the gases resistance to detenation, which means a heavier (thicker) fuel. 87 octane actually has more energy than 93 octane, but you will probably have detenation running it and the computer will pull timing making it produce less power.

Botch

 

I agree. Always run the lowest octane rating that the engine will allow. Any audible pinging and you should either adjust the timing or increase octane. Minor undetectable detonation the ECM will take care of.

Much better gas mileage from running higher octane? That's a new one on me

I have my 85 owner's manual, and there's no mention of the need to run higher octane gasoline for the TPI cars.

 

87 octane actually has more energy than 93 octane

if thats true then i leaned something new, i also diddnt know that you should run the lowest octane you can, well i know that for anyones wallet thats ussually the best to not run more then is needed, but i diddnt know you actually will get more power, interesting

 

You can advance the timing, and run a higher octane and gain a couple hp cannot you?

 

The BTU energy in 87 is the same as 92. Octane is the fuels resistance to detonation. It has nothing directly related to performance. If an engine doesn't detonate 87 octane then using 92 won't increase the performance.

As mentioned above, use the lowest octane that won't cause detonation.

 

It depends on how you plan to do that. If you are just turning the distributor, I would recommend against it because you might be getting more power overall but you might also be getting too much timing in one spot or the other. If you are doing it selectively thru the EPROM, that is a different story.

 

My Formula pings on hard acceleration when running 87 so I use 93.
I could probably back off the timing a bit, but that would lose me some hp.

 

I always use 93+ in the bird........I have had bad experience with pinging in the past (even on my carbed 305). I just feel more secure with 93 in there.

Later

 

I used 93, but they I discovered my timing was advanced a few degrees, and I set it back. Now it runs fine on 87
Heck with the money I save I could afford to blow up the motor and replace it because i'm using lousy gas .

 

The reason this happens on some cars is that by running low enough octane to cause knocking (detonation) will cause the computer to retard the ignition timing. Running around on reduced timing is not the best thing for effeciency. Also, if the motor would not knock at 1 degree less timing, you are better off to reduce timing at the distributor because the computer will often remove 3-4 degrees instead of just one. The reduce timing, will cause reduced cylinder pressure (the fuel burns too late and misses making peak cylinder pressure), this causes a reduction in engine effeciency and wastes some of the energy contained in your fuel (by not making max pressure at the correct time).

When I bought my 2002, it didn't run as I thought it should. So, guessing the dealer put 87 octane in it, I used 89 on my 2nd fill up. It was better, but not great and the fuel mileage was less than expected (who reads the book?). So, I switched to premium, the hp seemed to be where it belonged and fuel mileage came up even more (around town). Also, my 2002 Z will just "rattle" (knock) like mad at full throttle with anything less than premium in it. But my 3rd gen didn't have that problem. I do get better mileage around town on premium in the new car. However, I was going on a road trip once and the gas station was out of premium. Since I'd be cruising at part throttle on the highway, I stuck 89 octane in it. At part throttle, you won't see enough cylinder pressure to detonate and I got 27+ mpg with the cruise control set at 80 mph (it's an M6). As long as you keep it out of detonation, octane is unimportant.

Did any of that make sense? (it did as I typed it, but I'm not so sure now).