Insanely Low MPG, Can't Get a Clear Answer, PLEASE HELP

Hi everyone, I'm brand new here and want to be completely transparent in saying my understanding of Taco's is not very deep, or in general automotive repair for that matter, so bear with me. I will attempt to be as accurate as I can hoping some of you can help me identify my problem(s).

I recently purchased a 2013 TRD Off Road Sport 4x4, v6. It has a 6" welded lift with 275/60/20 (33") tires. It was previously in an accident on the back passenger side but all was supposedly repaired with factory parts and visually seems impeccable. I did have to change the brake pads, rotors, and calipers, when I first bought it but that was pretty well expected. So after getting it out of the shop I finally got to put it on the road for a few days and it rode very well (for my standards) and it came time to fill it up with fuel for the first time. The gas light had not come on but the gauge was reading right on the E, so I filled up and immediately made a round trip of exactly 41 miles. Upon return my gauge was already down just under 3/4 full. I'm now at 98 miles on this trip meter and sitting just a hair above 1/4 of a tank, meaning at bone dry empty best, I'm looking at 150 miles on a tank. Something is obviously wrong.

I know the lift and tires should affect mileage somewhat, but 8-10 mpg below factory? Surely not that much. I read some other posts in these forums about how gear ratios could be in play for part of the issue, but again, would the factory 3.73 ratio be enough with the tires above to hit the mpg that hard?

Here 's another wrinkle: I went back and looked at my bank log and the gas visit was only $34 and with prices in my town having been at $2.80/gal for several weeks now, that only equates to 12 gal or so of fuel, yet the gauge on the dash read FULL after the pump clicked off. As far as I know this truck is supposed to have a 21 gal tank. The 4-banger can have a 16 but not this 4x4 v6.

So does anyone have any ideas or feedback that might help? I'm willing to get the problem solved and I didn't buy the truck expecting stock level mileage or even "good" mileage, but there's a line there somewhere harboring on ridiculous and < 14 is it for me. Any help is greatly appreciated.

 

I would fill it back up first of all and see how much you actually used, it's possible it's just an inaccurate fuel gauge.

 

Fill it till it spills out the filler neck.

 

Looking at the needle position isn't going to cut it for calculating gas mileage. You have to write down miles driven and gallons filled every time you fuel up. That means fill it up until the handle clicks off, write down the gallons, reset the trip meter and track the miles. Next time you fill up, note how many gallons it took then look at your mileage. Do that for a couple weeks, crunch the numbers and then you'll see what you're actually getting

No doubt with your lift and tires you're getting fairly low mileage. The next step is to get some long term trims on a scan tool and go for a drive. The trims will tell you if the fuel system is struggling to calculate the mixture (indicating a problem) or you simply have a mechanical issue like tires, weight, lead foot, etc

 

Certainly not. It was just the first available means I had to get started and read what the situation. There were times in the last couple of days I could actually see the needle dropping as I was driving. It was literally mind-blowing. No signs of a leak anywhere (my first inclination), and various opinions from family/friends on lift/tires vs. gear ratio vs. mass air flow vs. gas gauge ... could be any or all of the above but it's definitely got me spooked.

 

Welcome, you will find a wealth of info and help here. Search feature will be ur best friend
Tacos seem to have finicky gas gauges
You will find most mentions for faulty gauge, pump or wiring, that said what else is there really
My 08 access cab at times would not start, I put two gallons of gas in and she fired right up. Went straight to the gas station and she would only take 11 gallons and be full. I ended up replacing the pump. When I pulled it the gauge indicated about 1/4 tank, it was more like at least half full. I put the new pump in anyway. Also replaced the vapor canister. Been fine since doing this.
if you replace pump buy a good name brand
Also when filling tank stop at the first click, don’t keep squeezing to add more. Good luck
I also drove around a while with a five gallon can so I could verify the low fuel light worked

 

Fuel trims are the key to separating mass air sensor, oxygen sensor, etc from tire weight, gear ratio, etc (fuel calculation issue vs mechanical issue)

 

I would first of all verify fuel usage/gauge accuracy using the method @b_r_o mentioned above, since the truck was in an accident it's possible the sending unit got messed up like on this member's truck.

 

One other thing when the low fuel light comes on u have at least three gallons in the tank

 

Fill it till it spills out the filler neck.
Do not do this you will fuck it all up real good

 

No please don't do this, you will destroy your EVAP system which can get quite expensive.

 

When you decide to buy parts check Rockauto

 

This isn't going to help you out but my stock 2010 averages about 18.1 mpg according to my Ultra Gauge. That was before I start messing around with the Ultra Gauge. I also have been religiously keeping track of my MPG and maintenance on an excel spreadsheet. My spreadsheet shows a range of 9.3 mpg to 23.9 mpg with an average of 17.7 mpg. The 9.3 mpg was during a run of zero to below zero temps with city driving. The 23.9 mpg was during a summer trip at about 65 mph and was never repeated. But you have a lift and tires/wheels to deal with that is to affect mileage. Even if you did the math by filling your tank and zeroing your trip meter, then at the next fill take your gallons and miles driven you couldn't get an accurate reading.
Look at anything that could cause drag, for example, brakes. Air filter? How clean are the MAF and injectors? I've had some success with Techron fuel cleaner in the fuel tank, but it's not a guaranty.

 

Ok, then don't do it. My bad.

 

Another thing I find is, with a full tank, stop at first click, If I’m on a journey I can drive 100 miles before the gauge starts to drop, not city driving.

 

OP, did you buy the truck from a private party? If so, and you have their contact info, call/write and ask if the gas gauge was inaccurate. If that's not an option, then definitely go on the assumption that it is until you get some data points from your fill-ups.

Congrats on your new (to you) truck. Show us a photo when you get a chance.

 

2010 Manual 4 banger...Sig shows my 19mpg avg...

 

Yes. Larger tires and a lift will reduce your mileage significantly. It will reduce it significantly more if you have a heavy foot and even more if you're doing mostly around town driving. 8-10 mpg below factory? Yes. It's possible. But in reality we're not even sure there is a problem. You're guestimating. and you're doing it with small numbers. You could easily be off 1-5 mpg.

 

HELLO NO FUCK THAT, its a yota buy oem only.

 

OP a 6in lift will dramatically lower mpg. My 4banger auto reg cab gets 15 city, epa is 16, but mines lifted and armor and a topper and etc. Seems about right for me. Any pending cel? You said you aint no shade tree mechanic……start watching diy videos on youtube and this forum is a lot of help, give her a tune up and as other have said fill it up till it clicks (dont overflow it, thats bad advice). Log your tripometer, when it gets to the E or the light comes on fill up. Get your tripometer miles and multiply it by the difference in tire size, look at your door jam thats your tire size and get the difference percentage and multiply it, add the difference to the tripometer, divide by how many tanks you put in, thats your mpg.