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

Yes!

The difference between 10mpg (awful) and 16mpg (not half bad) is only 3/4 of a gallon. Make it 200 miles, and now it's 7.5 gallons. I track my mileage every tank, rarely fill until it's at least down to 1/4, and I still probably get a decent bit of error from pump/filling variations. No way in hell you're getting anything accurate from 20 miles unless you go all Mythbusters and weigh your fuel tank before and after...

 

These 20 mile drives to determine fuel usage are ridiculous. Is the motor even up to operating temperature? That matters too.

Does the truck idle?

Are all 20 miles driven at once? Or is your commute to work 2 miles each day?

All of this could destroy your MPG measuring. Rub the tank closer to empty. I refill mine at 1/4 mark on the gauge every time. Puts in about 14 gallons. Tank is 21.1 gallons.

 

It’s always better to gets bigger sample size when averaging anything out. 20 miles is not enough for an accurate mpg calculation.

 

Hey OP in case it wasn't clear by the 142 comments, you should drive more than 20 miles when calculating MPG. Just wanted to make sure you didn't miss that.

 

This thread is worthless lol

 

On a related matter. I filled my tank. Backed up ten ft and then went back to the pump. I was able to put in 1/8 gallon. I believe I’m .06 mpg. I think something is wrong with my truck too.

 

The gearing doesn't work, next time go 10 feet forward and loop back in forward gear. Stay out of reverse.

 

This thread was like the final season of game of thrones.

 

Still didn’t see that you’re accounting for the larger than stock tires... again, won’t make THAT much difference, but it would change your numbers.

There IS a difference.

 

Got it, so I should drive 21 miles.

Serious note tho, y'all are dicks.

Ive taken larger sample sizes since this thread (100 miles). 12.566 mpg highway. Something is wrong, fuck off.

 

I agree with everything said as well as these comments here. Berryman's Chemtool B12 is AWESOME!!! It is more of a solvent, cleans the injectors, and breaks down water condensation buildup in your fuel tank.

I find that the fuel trim (i.e. Long Term Fuel Trim or Short Term Fuel Trim) are very important as it tells you how your computer is compensating for the fuel being used. So, if getting some sort of a "code reader/scan tool" get one that can do "Live Data". Plus you can look at other data like "Engine Load Calc". The cheaper scantools will cost you around $110 or thereabouts, but yet still very useful scantools. Personally, I would stay away from the Bluetooth $12 or so units, but I leave that up to the person themselves as I'm happy with my scantools and just don't care for the idea of $12 or THAT cheap of a scantool/equipment. Just my humble opinion on the really super cheap scan tool modules that you can get.

Anyways, just my 2cents and again, totally agree with just about everyone's input.

 

This is how I would calculate my gas mileage. I either go to the 3/4 tank mark or the actual half tank mark. Do a fuel to mileage calculation to ultimately get the mpg. I did this with my Honda Civic and it came out to roughly 34mpg, which is roughly what I SHOULD be seeing anyways. I was pretty stoked when the calculations showed that number as it was, sort of, proof that the numbers won't lie just as long as you're doing it correctly, of course.

But yeah, totally agree with this method!!!

Randy, how are your comms doing? Do you still have the CB setup and what not? Also, didn't you get a "new truck" about 2yrs ago or so? Anyways...

 

There's the way to get good assistance!

 

Well that escalated quickly. Nobody was saying, or at least most werent, that it would fix your mileage problem, but it would give you a better starting point. You just gained 3 mpg and told everyone to f'off, now your only about 4-5 mpg worse than average.

 

2 years to the day! Have cb in this as well with an nmo antenna, and a cheap handheld ham as my primary comms now.

 

Some of us are trying to help but you have yet to provide answers to questions.

You never answered what brand and model tire you have. You never answered the load range.

Please provide what type of driving (city/highway), what speed, etc.

FYI. You will catch more flys with honey than with shit.

 

This morning on my way to work (about 30 miles), I set my ODB Fusion app to measure the MPG for the trip. I started out at 0 mpg (obviously) and it got a little better the longer I drove. Once I got to work I was over 20 MPG, but it crept up pretty slowly. I was surprised how long the MPG remained in single digits. The 14 MPG that the OP observed for 20 miles is pretty consistent with what I observed as well.

 

Agreed that tire size variation from stock matters for calculations, but...there's no larger tire to account for here. OP isn't running 265/75r16, but 265/65r17 which IS the stock tire size for the TRD Sport model, which OP has.

 

Apologies, it wasn't directed at everyone.