Ok. I've made this thread before, no one has helped me. I am going to be specific now.

I get between 225-275 miles per tank no matter how I drive.

-New Plugs
-New wires
-New Battery
-New Belts
-New tires, light rims, properly inflated
-New fuel filter
-Just seafoamed my engine yesterday
-1.8 cam
-1.8 ecu
-CAI
-OBX 4-2-1 header
-2.5" full exhaust
-all fuels used, no difference
-berrymans in the tank right now
-clean-ish air filter

Why?

 

We have pretty small tanks, how many MPG is whats important.

Was it always like this or did it just gradually get bad-er. lol

 

Always this much... But there is tibs getting over 30mpg, i get like 18.... I'm going to do a compression test when im on my lunch tomorrow.

There's a couple things I'm thinking...
-Piston Rings, fried
-FPR bad
-Injectors bad
-Rail bad

A clutch won't make a fuel economy difference right?

bump

 

I do not see an oxygen sensor on that list. It can be on its way out without the CEL on. Just food for thought.

 

^Definitely. The check engine light doesnt need to be on for the o2 sensor to be going bad..and as you know bad o2 sensors give you shitty gas milesage.