Well I would start with checking and replacing the air filter.


I just made that guide real quick since I couldn't find a good guide for changing air filters.


Changing your spark plugs would also be a good Idea if they look original.
You could also try using sea foam, I would put a can in your gas tank when you fill it up, then get another can to do this procedure when the tank is almost empty.

Those are places to start, with no guarantees, but they are basic maintenance things that should be done to the car if they haven't been done already and they are fairly easy to do, a ~100 peice tool set from walmart will have everything you need in it for less than $40.

Cool. I'll try those. The sea foam sounds interesting.

Thanks for the guide. that'* actually very easy to follow.

Edit: We have some cops here that like to pull people over if their car is smoking. Some archaic law or something. How much will the sea foam make it smoke?

It will smoke depending on how much buildup it removes, sometimes it can smoke A LOT, so I would suggest trying to do it somewhere away from **** cops.

On flat ground my 4.6L V8 Grand Marquis would get about 27 mpg cruising on the highway. One hill drops the overall mpg to close to 20 for the distances I drive.

I know the Grand Marquis is not a Buick, but I honestly don't know what the mileage is on my wife'* Buick. All I know is that hills can have a huge impact on economy.

Seafoam, air filter, plugs, wires, clean oil, O2 sensors, MAF sensors are all good things to do. MAF sensors can be cleaned, BTW. In my experience, unless the maintenance has been really poor, these things won't account for more than 1 mpg or so.

However, I'm willing to be proven wrong. I must admit I haven't changed the O2 sensors on my Grand Marquis for over 100000 mi. The O2 sensors probably haven't been changed ever in the Buick with 180000 mi.

Maybe I'm just too used to I4 engines. This is my first V6 but I'm never going back. Even if the mileage does drop that much just from hills. I re-drove the route just to make sure and its actually more hills than not. I guess I never paid them much heed. I still find it odd though that even city driving I still get 20 mpg.

I know you've received answers and stuff, but I just want to throw my .02 cents in.

In my 02 SSEi I drive a 50/50 of highway and city everyday. I say this even though 75% or more of the trip is on a "highway". With driving through my neighborhood, the CRAZY traffic on the "highway"(lots of speeding up and slowing down), and driving on a military base throughout the day, it takes it'* hit on the mileage.

Now when I drive like this everyday, I get about 20-21 MPG and that'* letting it warm up every now and then if I have to take my son to daycare. On straight highway driving, 70+(usually 75 on your typical interstate), I'm pulling just 26 or so.