I have a 1995 Z28 which still is in great condition. The problem though is that I'm getting 11 to 12 miles to the gallon city and just about 20 highway. But just two years ago I was getting 17 mpg city and close to 28 hwy. Everything is stock and mechanics say that it's just getting old. I refuse to believe that because I've known people with these cars running over 200,000 miles and still get at least 16 mpg in the city. Mine has only 115,000. I got a tune up last year and never saw a change in mileage and have been trying different mechanics ever since. And all give me the same old crap. I think it just so happens that all these idiots in the San Fernando Valley see too many rice burners and can't figure out a real car when they see one. I even think they just did the tune up wrong! So someone please give me suggestions as to what may need to be checked out and fixed. It would be greatly appreciated since if I can't fix it I will need to sell the car for lack of funds. And selling my car cannot become the option, so someone please help!!!

 

Check for exhaust leaks before the o2 sensors, that will cause these cars to run rich and use more gas. Also, are your cats clogged? What kind of mods(if any) are on the car?

 

I have no mods. And I don't think the cat is clogged, but have not checked, so it could be. And I had it checked for leaks before the o2 sensors not too long ago so that isnt it. Any other things?

 

What brand o2s?

 

Oh, that I don't know.

 

I put bosch on mine, and gas mileage went down. Take your MAF off the car and see if it is dirty. When mine was dirty, i lost about 60 miles to the tank.

 

I don't know how to do that. Take it off I mean. I know about cars, but I rarely jump under the hood of this one so you would have to explain if you don't mind.

 

Check for trouble codes. Also it might be a long shot but check the vacuum line from the fuel pressure regulator to the intake. Mine broke once and was pumping gas right into my intake. it sent my gas milage to hell and made me fail emissions.

 

Just look for the silver thing between the rubber intake elbow and the air intake. It is two band clamps you can undo with a flathead screwdriver and then it comes out.

 

Were the O2 sensors replaced when the car was tuned? If not, O2 sensors get coated over time and tend to make the car run rich. Replace with AC Delco O2 sensors.

 

Ditto ..... Chances are the O2 sensors are original, and with 115,000 miles, they need to be replaced. Replace them with stock AC Delco replacements (can be had from a dealer) and I bet your milage goes back to normal.

Thomas.

 

Soft tires can cause this, check they are up to pressure.