I always run premium or Super unleaded with a minimum ocatane level of 91. One place I filled up during the trip only had 93 octane. We did have two suitcases and some other stuff but I wouldn't say I was overloaded at all. On the trip back we had a lot more stuff and only got slightly less mileage and used the AC most of the trip.

I was running between 65-75mph most of the trip so that could be part of the problem. Like I mentioned in other posts, this car is fully tuned up with all new ignition parts except the ICM and coils and I used all AC-Delco stuff. It also has all new filters and I changed the tranny fluid with the new Dextron VI fluid. It also has new tires and had a four wheel alignment done when the tires were installed. The intake manifold gasket and valve cover gaskets were also recently replaced.

I can't think of anything else that could be replaced that would affect mileage unless my catalytic converter is going bad but the car has plenty of power with no CEL.

Before the full tuneup, I was only getting 23mpg on the highway so its improved a little. I guess I'm just going to have to live with it. Thanks for the replies.

Wayne

 

I wonder if u have a caliper hanging up slightly, u may not feel it while driving but it may be enough to effect gas milage. Press and release the brake a few times then jack it up and see if one wheel spins harder then the others

 

I will look into that, thanks.

Wayne