I started burning premium about two months ago, when I also started using synthetic motor oil. Between the two, my average mileage (without changing my driving patterns) went from 16.4 to 18.6 mpg. Factoring in the fuel I save each week, the increased costs of premium (about twenty cents/gallon) is more than made up by the decreased costs of filling up.

The LD8 has a compression ration of 10.5 to !. So yes it can benefit from premium gas. Sure not as much as higher rated ones. Will is right about needing a scan tool to really prove this out. My GXP likes premium. It runs better on Premium. The mileage is a little better but I haven't tried to figure if cost effective. I always have my foot in mine and dont want KR damage, I'm wearing the engine out prematurly as it is and look the other way while I pump in the 91/93

The only thing I run in the GXP is 91 (we dont have 93 here) but I think that is more of a carry over from the 95 bonn. than anything else

It sounds like I should give the 93 a try. I average right about 19 with 87 and I fill up about twice a week so it shouldn't take long to tell if there is a difference in economy.

How many miles on your car man, the MPG should keep going up as the engine loosens. I am at a little over 24mpg on the highway now. The car doesn't see enuff city lately to know that number. I've hit 10.8 MPG avg. in town emptying a tank of nitrous in a night. The car can really vary.

I bought it with 27k on it in April and I am almost to 49k. I drive 30 miles each way to work on the highway but do quite a bit of city driving between offices and tend to be heavy on the gas. I have gotten as high as 24 mpg on the highway from Detroit to Kalamazoo (130+ miles) but that was with cruise set at 70 and it wasn't fun for me. I normally drive between 80-90 on the highway to and from work and like I said pretty heavy on the gas. I normally average around 19 the way I drive but I have seen as low as 16 with mostly city driving.