*Very* bad gas mileage in my truck, advice needed.

Show us your math you’re accounting for the 265’s? Pretty sure stock are 245’s.

Edit, not that it would account for only getting 10mpg, but it wouldn’t help with your numbers.

 

Unless he's running like 10psi his tire pressure won't cause him to be getting 10mpg. Do you live in the mountains or a very hilly area with windy roads? Could be lots of things, but I'd check MAF anyway and checking tire pressure can't hurt, may gain 1 or 2 mpg if pressure is way off.

 

All of the above is good advice....some other pointers:
- Are you RPMs staying under 2000? Tacos really burn gas when you go above that. You can only go about 65-70mph...any faster and your RPMs are going to be over 2000
- I will go ahead and ask..are your driving like a teenager or adult?
- I would try to empty your gas tank as much as possible (could have some old junk in there) and only use Chevron gas (That is the gas all manufacturers use to get the MPG on the window sticker. If not available Shell has techron in it and is second best.
- Are you 100% sure you are not in 4WD? Engage it and make sure the light goes on and off and you can feel the difference.

10 is really low, you should be getting at least 16 in mixed driving.

Good Luck and keep us posted

 

By ODM do you mean OBD? If so, is the truck throwing any engine codes? What's the long term fuel trim %?

 

I average around 15. Can get 17 on the highway, but I'm running 35s. 10 is ridiculous for regular non towing non uphill driving

 

Sticky front calipers.

 

Very possible.

 

Not totally relevant but I would just like to add that RPMs alone aren’t what causes bad mileage, it’s engine load. I found if I leave it in 4th gear (I’m a manual) and cruise at 3k rpm, my engine barely has to work to maintain 65mph. I gained 2mpg by doing that and can get 15.5 mpg on the highway. That’s taking the larger tire size into account. Before when I’d be in 5th gear cruising at 70 with rpms around 2300, I’d get about 13 mpg and the truck had to work a bit harder. I use my ultragauge to track engine load percentage.

Again, not exactly relevant but wanted to point that out.

 

Ive never gotten less that 13mpg and I drive like an asshole. You stated the tires have the "correct psi", but what is that? 32? 38? Do you have a tire pressure guage? IMO if they were low enough to hurt your mpg, the tpms light would be on indicating a lower than optimal PSI in one or more of your tires. You're still on the factory sized 265/65/17 that sports come with so no need to adjust for tire size. Don't worry about changing your rear diff fluid unless you're really bored.

I'd definitely start with cleaning the maf sensor and the throttle body as previously mentioned. Use sensor safe cleaner and also use a few cuetips, and gently clean the coils inside the maf. I cannot stress enough to be very gentle as you can easily break the coil and render the maf useless. Basically as long as your not ram rodding it in and out round and round you should be fine. A few beers or drinks will help to take the edge off, but if you don't feel comfortable doing that I'd suggest purchasing a new maf to be on the safe side.

Alignment specs and wheel bearings will also affect your rolling resistance if either or both of those components are out of wack.

Only other thing I can think of would be to pull the dip stick and smell the oil. Does it smell like fuel? You may have a stuck injector if so.

 

Does it come up to temp? Thermostat stuck open

 

Did you start with a full tank? How many miles did you drive? How much fuel did it take to fill up the tank? Let someone else run the numbers for you.

Even if you're running in 4X4 that is only going to be 1 mpg, 2 at most. The odometer may not be calibrated correctly and you could be driving farther than you think. Does the truck seem to have enough power, or is it sluggish. Could be a catalytic converter going bad.

 

I was thinking the same thing, but I'd expect to see some sort of emissions code surface if it was that bad.

 

What speed are you driving at?



It could be a combination of a bunch of little things, adding up to kill your mileage!

 

Are you sure your truck is shifting into overdrive gear or is it staying stuck in a lower gear? Are any of the wheels VERY hot or smelling like brakes or hot steel? Parking brake stuck on? Is the exhaust odor very strong? I would advise you to get it to a shop you trust and ask them to look at it. You will be advised to spend lots of money throwing parts at it blindly when it may be a relatively simple problem or a major one you will not find after all the time, effort and money. It also may be the way you drive. Drive like there is a raw egg under the gas pedal for a tank and see if it improves. If not, then visit the shop.

 

One other thing to try is take a drive with your obd scanner hooked up and if it has the ability to give live engine data observe what various sensors of the engine are displaying. This works a lot better with 2 people and the data observer in the passenger seat. Looking at things like engine coolant temp, catalytic converter temps afr and other vitals can help to narrow down where the source of our poor mpg is coming from. Although if you aren't familiar with or understand the data being shown to you, it probably will seem like a foreign language and won't be much help.

Good luck.

 

What I said.....mine seized a bit waiting for frame replacement, then new ones again about 15 months or so later. They didn't lock up, but enough to effect mileage badly

 

Curiosity definitely has me watching where this goes...

 

No codes what so ever.

Yes, OBD is what I meant, I'd love to make the excuse that autocorrect got me but I think I just had a brain fart.


To the person asking about it being stuck in 4th instead of shifting to over drive, I don't believe so because when I throw it into 4th it definitely downshifts, so there's no way it wasn't in 5th. Also, no codes are being thrown at all.

Next update, I was wrong about the air filter being new, previous owner lied to me, I replaced it with a K&N. Too early to know if it's made a huge difference. Checked the calipers, I don't think they're sticking. The engine is not running rich. On Tuesday I'll be cleaning the MAF sensor, will update following that.


Also, to the person who asked me if I'm sure I'm not in 4x4... I'm stupid, not blind. Yes I'm sure.


All that said, reading through all this feedback is helpful. I'll keep y'all posted soon.

 

Berryman's Vitamin B
Pour a bottle in your tank when you fill up next time.
Check to see if you are in ODO Kilometers instead of miles.
Headscratcher!

 

What???