my 96 EJ8(4 door EX D16Y8) is getting 26mpg highway and 23mpg city. This seems very poor. It is an automatic but I've heard that it's common to get 35+ mpg highway. It has 134k miles. I just replaced vtec solenoid gaskets, oil pan gaskets(and oil obviously), exhaust gaskets between header and downpipe, and pcv valve. The car is no longer leaking any oil. I thought for sure I would see a mpg improvement but I did not. I ran the tires at 44psi and got 24mpg then I ran them at 36psi and got 26mpg. The car has a cold air intake but other than that it is stock. The only thing I can think of at this point is the O2 sensors. But there is no CEL light on. what can I do??

 

o2 sensors should be fine. They either are working, or they are not IMO.

When was the last time a tune up was done? Dist cap/rotor, wires/plugs? 26mpg for an AT isn't terrible. Many Autos get less mpgs than manuals and the best I ever saw when I had a stock motor (manual) was 28-29 on the highway with the D16y8. The D15z1 and D16y5 reguraly see 35+ since they are lean burning motors.

 

guess i should have mentioned that the valve cover gasket was also done about 5k ago and plugs/wires done about 1k miles ago. Not sure when the last time the distributor cap was replaced. I know autos get less mileage but i still see people getting 30-35. I would love tgo get 30mpg at least, is there anything else I can do? Should I go back to the stock airbox? I'm not sure how to check the timing? Is it hard to do? I've read about people having their timing slightly off and getting 5-10mpg less than they should. I've also read that O2 sensors can go bad and not throw CEL codes. They chould be replaced around every 70k miles but i doubt they ever have been. I'm just hesitant to do it because they are not cheap.

 

Oh we also had the A/C on the whole time we were testing the mileage(550 mile trip to FL) could that make a big difference?

 

Woah! If you get 26 mpg on the highway, thats way too low. You should get a tuneup or something.