Well, I decided to record my mileage since the last tank-up and it isn't pretty. It looks like I'm gettin 15.1MPG as of now. To my understanding I should be getting at least 18MPG? This is all city driving and the O2 Sensor was changed after getting a code 44 a couple thousand km'* back. Plugs are also pretty new, the rest of the things that have been done to the car are in my sig.

Any ideas of what might be causing this?

Do you have a heavy foot? Is this mostly city driving?

I'm thinking the biggest cause of poor fuel economy is needing a tune up, but you have that covered. Clogged cat perhaps? EGR Valve look alright?

When you did a tune up and the CAI and all that work, did you reset the ECU, by chance?


-justin

Heres what I would do. My 90 gets 19 -20 around town.
Install fuel injector cleaner every 6 mo.
Check the TPS voltage at idle. Key on, motor off. should be 4.2 -4.6v.
clean throttle body, IAC, & MAF sensors.
Check if front calipers are sticking, if so clean & lube slides with silglide.
And of course filters filters filters, fuel and air.
And if they are using ethanol in your fuel expect a 2 MPG drop.

To test the calipers, put the car in Neutral, and set the E-Brake. Raise the front end so the wheels are above ground, and rotate the wheels [tires and all]. You should be able to rotate it fairly freely. If you do it in park, this will not work.


-justin

Driving habits make a big difference as does the late lockup (Reatta locks up at 46 mph but Bonne doesn't until after 50. I mean to fix that someday as there are a lot of 45s around here).

Am getting 18.7 mpg on current tank but all short hops, with 50% Interstate I get over 20. Spouse has a heavier foot and gets less.

Miles also make a difference - after 100k the timing chain has stretched retarding the already ded cam.