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

How are you figuring mpg?

 

Fill the tank, drive 20 miles, fill it again, measure how much was lost vs distance traveled. I rinse-repeated this process 3 times to make sure.

Im driving like a reasonable person would.

 

I think you would have more accurate results if you let it go roughly 3/4 a tank

 

I agree. Fill the tank up until the pump auto shuts off. Drive until you have about a 1/4 tank left and fill back up until the pump auto shuts off.

Miles traveled/gallons put in=more accurate MPG

 

This is me. I get 13 mpg every single time

I use @EatSleepTacos method for figuring my mileage.

 

Are you dividing miles by gallons example 300 miles took 10 gallons to fill back up = 30mpg
10 is crazy bad my 15 average is 16 to 18 combined and 21 straight Highway

 

Hell I get almost 15 pulling my bass boat .
I’m in for brake stuck or your figuring it wrong

 

Most injector cleaners are snake oil. Seafoam is good stuff but best used through the throttle body to help clean out carbon buildup.

For a fuel system/injector cleaner, get a can of BG 44K...probably have to order it online.

$25 BG 44K Fuel System Cleaner Power Enhancer 11oz.

https://www.amazon.com/gp/aw/d/B00DDVU6EI?psc=1&ref=ppx_pop_mob_b_asin_title

Not as cheap as the stuff you see in stores but it's proven...truly clogged injectors though need to be taken off and cleaned by hand, or professionally.

I would also get your ECU scanned for any pending check engine light codes. If your mileage truly is that horrible you might have issues with an o2 sensor or maybe the cats, in which case a check engine light will likely appear in time.

 

You really need to do a couple of tank fillups keeping track of the mileage and total fuel. Your fill point will be different each time depending on how the fuel splashes arounds and stops the pump so 20 miles is not nearly enough to get anything accurate. One tank is not enough either, you need multiple tanks. Here's my last 7 fillups and you can see the mpg change as we changed from winter to gas to summer gas and the weather got warmed also helping mpg. What you can't see is that I started towing my 2 boats pretty often on the 3rd tank and the mpg still kept going up so it might have gone up even more without the towing. I have the 2.7 with auto and 33" tires with 3" lift and do local driving so my mpg is lower than a stock truck. Still, your 10 mpg sounds way off so something must be wrong. How does your tire wear look?

miles - gallons -- mpg
180 --- 12.92 --- 13.932 (Feb)
135 --- 9.08 ---- 14.868
182 --- 12.31 --- 14.785
117 --- 7.66 ---- 15.274 (Apr)
163 --- 9.76 ---- 16.701
173 ---10.345 -- 16.723
252 --- 14.79 --- 17.039 (May)

 

Don't different pumps shut off at different times when refilling? so if only driving 20 miles and then refilling, the math could be really off because the added fuel is not the same from pump to pump. I agree with running the tank to at least a 1/4 tank remaining and refilling. Even one test on that could make a difference.

 

It doesn’t matter when the pump shuts off because you use the pump meter to show you the volume of fuel pumped.

 

Right, but if the pump shuts off, then you keep trying to top it off, it's going to add more volume of fuel which will adjust your numbers. Not saying it's going to make a big enough difference to cause 10 mpg but with other things included, it could affect it.

 

I see what you are saying now. I guess the bottom line is 20 miles isn’t nearly enough to make the difference in tank volume negligible.

 

Yeah i'm just spit balling ideas.

My rationale was if he drives 20 miles, fills up with 2 gallons, he's at 10 mpg. lets say he tops it off and fills up with 2.5 gallons, he's now at 8 mpg. But yeah, we need to see more sample sizes of way more than 20 miles to see a bigger picture.

 

Why doesn’t OP go for longer than 20 miles. Cherry picking short stints is a great way to show really good gas mileage or really bad. Small sample size means much greater standard deviation.

I’ll bet it jumps precipitously.

Also, OP - lose the K&N. Tacoma’s are already notorious for ingesting dirt - no need to make the filtration situation worse.

On the sticky brake thing - Do the front or rear wheels feel exceptionally hot after extended driving?

There just aren’t that many parts that could cause THAT much parasitic drag. It’s really either the brakes or a fuel mapping/tune issue.

Cleaning the MAF and TB and taking the truck in for a brake service front/rear are going to be your first steps.

 

going only 20 miles is the first thing that makes sense and could cause 10 mpg. 100 miles minimum. it would at the very least give you a more accurate determination of where you are.

 

I've gone through around 5 calipers on my 2006. Sometimes the drag is so slight that you barely notice and the wheels don't really heat up that much, but it makes a big difference to economy. I would definitely be looking there.

 

Are you filling at the same pump? That will have a factor. 20 miles is too small of a distance to even worry with calculating. Also, what brands tires are you running? Should see a load range on the tire as well. Different load ranges and manufacturers weigh differently.

 

Don’t know if this was asked but how much crap do you have in your truck? I use my truck for work and carry about 200 pounds of tools. Wich can make you loose 1-2 mpgs Do you have aftermarket metal bumpers?. You can also reset the ecu take the battery cables off and touch them together and start fresh.

 

Calculating mpg over 20 miles = Fail