1) Get the tire pressures up to at _least_ 35 psi cold pressure; you'll feel the difference in rolling resistance.

2) Oil and filter change

3) New oxygen sensor, if you can't remember the last time yours was ever changed. With the right socket and a couple of extensions, you'll have this done in less than an hour. AC-Delco is recommended over Bosch.

Mid-range gas might be a good idea if the compression has gone up due to carbon buildup in the cylinders, but I wouldn't bother with premium unless the car is labeled for it.

The tire pressures and oxygen sensor will probably have the biggest effect on gas mileage, especially for a fully-loaded car.

Just got home. Wasn't able to do anything to the car like I wanted, but I didn't have any problems. With the 4 of us in the car, 32psi in the tires, cruise set at what ended up being 77 in MI and 70 in OH, plus it being set at 60 on the 60 or so miles miles of two-lane road we had to take each way, it averaged 29mpg...this is with the AC on medium because evidently my friends are all really warm...I was freezing, but hey...whatever. I also had to change freeways and merge onto others a half a dozen times each way, most of which I was at WOT while merging, and I also passed a few people on the two lane each way. I did notice that the longer I drove the car the better it ran, at the beginning of the trip it didn't seem to have much power, but on the way back, after merging into traffic and passing people a few times at WOT it started running better. Maybe the engine needed to be cleaned out or something.

I would've put the tires higher, but the max pressure stated on the sidewall is 35psi (they are REALLY cheap tires, which is why I think something is wrong when it can't even get one single chirp out of them), and the manufacturer recommended inflation is 32, so I figured I would put them at 32. I can't imagine that 3psi would make THAT much difference. I can change the tire pressure in my car 10psi and not notice much, if anything at all.

Anyways, I appreciate the suggestions. I will probably change the plugs/wires/coils pretty soon here. The 02 sensor has not been replaced since we bought the car 25k ago...so it probalby does need one. My guess is that its the original...oops.

Shawn

Heck, 29 mpg is outstanding under those circumstances, and you're probably right that the engine seemed to run better as you got further into the highway miles. I would put a new AC-Delco oxygen sensor in whenever it'* convenient, even though the old one seems to be functioning more-or-less okay at the moment, since they don't improve with age, but otherwise I think you're probably getting as good a mileage number as you're likely to see for highway use.

I think new ignition components and oxygen sensor might help your around town, stop-and-go, short-trip gas mileage a little bit. How about measuring your current city mileage through a couple of tankfuls first, then swapping in the new components and see how that affects the numbers?

I don't drive the car normally, its my sisters car, so it would be difficult for me to keep track of mileage, and since its my sisters car, I'm not that worried about it much. What I'm worried about is that the car seems a lot slower than her other one was, or than this one used to be...maybe I'm just used to my car, I don't know, but I want to put new coils/wires/plugs on it to see if it makes it any quicker...if not, oh well, I can't imagine it hurting anything unless one of the coils/wires/plugs are bad.

I am definatley not complaining about 29mpg. My smaller lighter car, with less miles, that is maintained a lot better, with a smaller engine, wouldn't have gotten that good of mileage, and I have to run premium. I probably would've averaged about 25 or so...its gets 32mpg on the freeway with just me in it, but with 4 people, a full tank of gas, etc..., I'm sure that number would go down, and then factor in the merging and everything, it would've definately been a lot lower.

Shawn