From when my low fuel light goes on, to fillup, one click on the pump, is 19.7 gallons on my '97 3.4 4 x 4 automatic. This particular tank I got 248 miles. A whopping 12.6 mpg! I did two highway runs. One was 77 miles, the other 43. The rest were local short trips. Warmups in the a.m. were about 3-4 mins. I'm easy on the pedal, really. Just before this last fillup, I swapped out both 02 sensors. The plugs have 20K miles on them. The truck runs like a top. I haven't cleaned the MAF. It's the jet engine type with the sensor riveted in. Since I'll have to blindly flood the tube with cleaner, I've been reluctant. Mostly because, when I do it, I'll want to let it dry out for a few hours before I reinstall it. I just haven't had the time. Could a dirty MAF be what's killing the MPGs? A dirty throttle body? Do the 02 sensors need to break in, or does the ECU have to adjust to them ? The tires are stock Michelin LTX MS @ 34lbs. The last tank was 91 octane. I just refilled with 87. Maybe that'll help?

Any thoughts? <img src="/forums/images/graemlins/confused.gif" alt="" />

Did you reset the ECU? If not, you'll probably need to disconnect the battery fer about 30 min or so. That should allow the ECU to relearn the system again... <img src="/forums/images/graemlins/wink.gif" alt="" />

Consistent gas mileage isn't a strong point on my 97 3.4 auto 4x4 either. Some times I get down to your range.

What I have gradually observed is the gas mileage is hyper sensitive to city type driving and brisk acceleration.

It takes very little load in the bed or a trailer to drop gas mileage as well.

I get a pretty consistent 15mpg and I'm lifted on 35's, have a 5spd, and I'm not particularly easy on the gas pedal. You're apparently stock with an auto (higher overdrive gear), so I'd expect you to get significantly better than I do. My driving is primarily highway/commuting though, so that would make a difference.

I would do some basic cleaning/maintenance: Clean the MAF and throttle body (don't worry about letting things dry out, you're not going to hurt anything), do the Sea Foam treatment on the intake, and then reset the ECU (pulling the EFI fuse for a minute is sufficient). Make sure your air filter is clean and nothing is blocking/restricting the intake. The 87 octane should help a bit too.
Also, go through the rubber intake connections/joints and look carefully for any cracks or looseness that might cause a leak.

Is your truck going into overdrive and locking the torque converter on the highway?

My 97 seems to be just as finnicky. Colder temps definitely affect it but sometimes there doesn't seem to be anything to point at. I have an old Civic as my daily so it may sit for 3-5 days not being driven. If I drive it daily the milage seems better and there is no fuel leak. My last tank full was 17 MPG. The one before it 14. Dunno.

I always attribute a 2-3 mpg decline during the colder months to Winter-blend fuel. We see it in all of our vehicles. Later in the Spring it pops, no pun intended, right back up to where it was the past Summer. Brew <img src="/forums/images/graemlins/cheers.gif" alt="" />

Sounds like I might need to do some of the same maintenance on my 97 with 80,000. Was getting pretty good milage las summer. Then this fall moved to a little larger tire. Had attributed my decrease in milage to the new setup, but maybe poor gas, cold temps and dirty parts are also party to blame. I dropped from 18 mpg to more like 12 with just a 285 75/16 tire? I wouldn't think so..... <img src="/forums/images/graemlins/angry.gif" alt="" />

You got air in them new tires?

To hell with the numbers on the b-pillar, they always seem way too low.

They are for the STOCK tires..I run 41 in front and 43 in rear and get excellent mpg, 17.5ish.

Gas mileage is a sore spot with me on this truck. 2Wd with 80K and top notch maintenance using Genuine Toyota parts gets me 15/18- empty. Drops liike a stone with any load or even an empty trailer.

This and all the little but expensive annoyances assure my next truck will be a Chevy.

My 95 Chevy 3/4 ton Suburban gets the same mileage with a 6.5 TD at 260k on the clock. It has never seen a wrench.