Poor gas mileage...tried almost everything

I bought a 98 tacoma 2.4 5 speed a few months back as was getting terrible gas mileage (17-18) even with premium. It was throwing an O2 sensor code and throttle position sensor code so I replaced the pre-cat O2 sens and cleaned the throttle body. Mileage went up to about 23 and lights didn't come back. Still wasn't happy so I ran several cleaners through the system (including seafoam), change the air filter, cleaned the MAF, replaced the jiggle valve, replaced the spark plugs and wires and replaced the vacuum hoses, not to mention keeping the tire pressure up and an alignment. So far the light hasn't been on for prob 500 miles but still can't get more than 25mpg even with Chevron premium on the highway with a light foot. My old 96 Taco got 30+ on the highway.
I have thought about changing the post-cat O2 sensor and throttle position sensor but without a code I don't want to throw away good money. Any suggestions??

 

don't waste your money on the post cat sensor. First of all, it doesn't affect fuel trim. Plus you would have a code saying "catalyst efficiency below threshold" or something similar. It's only job is to tell if the cat is functioning. If your TPS is bad, it could affect mileage.

 

What size/type of tires?

 

what is the long term trim reading ?

 

a gummed up/bad coolant temp sensor would give you shitty gas mileage...

 

If the engine's not knocking you aren't doing any good putting premium into it, and if you want good MPG's get a car? 25 is decent for driving something with the aerodynamic efficiency of a brick...

 

I wish my 96 got 25 mpg!

 

The best I ever got with my '99 Extended Cab 2.4 automatic was 26 MPG. The worst was 14 MPG. I think you're in the ballpark.

 

25 mpg during crappy gas season isn't bad at all.

My old 96 2.4 regular cab 4x2 5 speed got 30 highway. The 98's may be a touch heavier plus that engine is probably 20hp down from new just from being that old. Heavier / more aggressive tires could contribute as well.

I wouldn't worry about it too much.

 

your mpg is average for what it is. shouldn't be anything wrong

 

Its got stock tires. Might take a look at the coolant temp sensor. Its not bad mileage. Just wanted to know if there was anything else obvious I'd overlooked.

 

i think you guys getting over 30mpg's are crazy. not impossible just if i had to drive that way i would shoot myself in the face (alot). i shift at 2000 rpm and i squeeze 24.6 mpg but my drive is very harsh.. i think 30 may be possible but i cant see these trucks getting any better. just my opinion.

 

how do you get 24+ mpg?

is it all highway driving?