I've always been so curious as to what exactly the difference is between all the gas companies. I try to stick with Shell or Chevron but is it worth the 10 or 20 extra cents per gallon?

Also, I try to use premium all the time but my 280 seems to run fine with regular. I don't drive it very hard. Does the Z need premium?

Thats a good question. I put premium in the 350 because its recommended but I put just 87 or 89 in the 240. Haven't noticed any ill effects.

I am running a '82 ZX motor with slightly higher compression. 9.5 to one , I run the mid grade gas and have tried regular with no perceived ill effects. As to the different brands I can see no difference in performance or mileage. I haven't done a comparative testing on a dyno or anything. Just seat of the pants observation.

Gary

93 only in my girl. She doesn't like the lower grades.

The lowest grade gas that you can run with the optimum amount of timing for your particular motor will make the best power. Dan Baldwin proved this maybe 4 or 5 years ago with back to back dyno tests with 93 octane and race gas on his stroker with OER carbs. If you want to do some digging you might be able to find the dyno sheets.

I ran 87 in both the 1978 280Z (12 years), and the 1979 810 (6 years) with no ill effects when I had them.......

My Z wants to ping a little at lower RPM's with lower octane fuels... I try to fill with 91 or better since it only costs about $1 more to fill with premium.

I would think that a stock engine would run better on regular gas but who can find regular gas any more.

I use the lower grade at any station in my 280 and get great milage and power for the straight 6.

I also have an 07 PT cruiser that has a MPG guage. I have not noticed a milage difference from station to station. I have not realy noticed a difference between lower or higher octane either.

I also get a small amount of pinging (?) at lower RPMs on regular (87 octane). I normally would hear it accelerating up a hill in the 2000-3500 rpm range, it would sound like a rattling sound from the engine bay. A tank of premium fuel later, and I haven't heard it since. *shrugs*

I buy most of my gas at chain of convenience stores called QuikTrip. They're based in Oklahoma but have a lot of stores in Atlanta. It's not Exxon/BP/Shell/Chevron and the gas is almost always less expensive than those name brands. The interesting thing is that they actually encourage customers to not waste money on premium if it's not required by your engine. Have you ever seen a company this honest in advertising?

http://www.quiktrip.com/gasoline/myth.asp

This topic comes up every summer...

Gasoline comes up through the same big pipe from the same few refineries. The difference is the additives and octane boosters that the distributors put in before you pump it. I had some pinging in my engine before I gave it a couple treatments with Seafoam (i.e., it was decarbonized) but now it is great on 87 or 89 octane.

So if you have a stock engine with 8.8:1 compression, and not a lot of carbon buildup and everything is adjusted right then you'll not be needing higher octane.