Gas Mileage Difference
 

I have a '97 SE with the standard 3.8. no upgrades. all stock. i get about 280 miles to the tank, about 17 to 18 mpg on average from what i can figure. all in town driving. I found a '97 SSEi with standard supercharged 3.8 on my local craigslist and he said his car got about 480 miles to the tank. Why such a big difference? and especially since his car is supercharged and should be getting worse gas mileage? just wonderin. (not sure if this is correct forum to place in?)

It all depends on how you drive. I'm getting about 18 mpg right now. When I drive easy and it's summer I can get about 27 mpg. There are several things that can effect millage. Air filter, spark plugs, spark plug wires, MAF, O2 sensor. Also, a supercharged engine uses premium gas and can get better millage from that. I get about 2 or 3 more MPG with 93 oct.

Seems you should be able to get better than that around town. Air filter, plugs, and wires all up to snuff? As for the 30MPG average in a 97SSEi, I call bullshit LOL. I think he's a ranking your chain. ;) With the V8, I get 10-14 cruisin, 17-18 civil intown driving, 23-24 Highway w/cruise on.

im in the process of doing a tune up on my car. air filter, oil change, plugs and wires, and possibly coils on the list. and i was kinda thinking bs too. i could see if it was around 100 miles more but 200+ miles more when his motor is supercharged and mine isnt is a little questionable.

You can look up the "test your coils" in the "How To" section. No sense in replacing unless needed.

just tested them today actually. https://www.gmforum.com/t278710/

ive been havin some problems with mine. thats my post about it all.

Changing and maintaining your fluids, changing the plugs and wires will also help a lot. New coils will also help if your old ones are getting tired. But don't forget about that O2 sensor. That's one of the sensors used to tell the computer how much fuel to pump. Clean the MAF as well. This also tells how much fuel to pump. A tired old O2 sensor will cause yoru millage to drop over time. I think I added close to 4 or 5 mpg when I changed it out. Just do NOT get a Bosch O2 sensor. They have proven to not last.

I have a 97 Bonneville SE and I average 18-20 mpg in the city, and 25-28 on the highway. That was after gutting the airbox, new fuel pump, new fuel filter, new plugs, new wires, and of course a new air filter. I took the car round trip to Denver CO from Kansas City MO and I got 350+ miles to the tank.

where is the o2 sensor located on a 97 bonneville se

Here is a close up of one. It's on the rear exhaust manifold right where all the pipes come together.

http://i300.photobucket.com/albums/n...r/P9120005.jpg