How bad is bad mpg in a 4.6L 4wd?

After about a month of bouncing back and forth between a used Ford or Tundra, I let my buddy with an '11 4.6l DC 4wd talk me into choosing the Tundra after he stated he consistently gets 20+mpg driving all around Utah and CO as a sales rep(with a topper, roof rack AND a big storage box on top). I found an '11 4.6l 4wd with 80k on it that seemed like it was very well maintained and bought it. Stock everything, and brand new 255/70 road-friendly tires, too. I drove it like a grandma for the first tank, which consisted of about 90% highway miles on 2-lane mountain roads with speeds in the 45-65mph range, and was really hoping to at least get the EPA estimated 19mph, if not something like what my buddy claims to get. After the gas light came on 275-miles into a full tank of premium gas, manual calculation showed 13.8mpg.

Air filter looks new, tires are at proper pressure, I disconnected the battery to reset the ECU when I first picked it up, and the oil is fresh. Am I missing something? After a search spree on "Tundra mpg" I see a lot of 5.7l owners get about this as an average, but is this as good as a 4.6l engine can get on mellow highway use without hauling anything or having a headwind, etc? Or is this a sign of something needing attention? I realize it's a truck and wasn't expecting Prius style fuel economy, but at the same time, I sure as sh!t wouldn't have opted for the smaller engine if it's no better at sipping fuel than the 5.7l versions. Thoughts? Hoping it's something common like simply needing a fuel filter(my Sprinter used to creep down into noticeably lower mpg's when the fuel filter was due for a change). Thanks in advance!

 

I started with a full tank, drove 283 miles, then filled it up with 20.36-gallons, which equates to just over 13.8mpg.

 

Well, good to know I wasn't running on fumes. But, I'm more concerned about the poor mpg than miles per tank.

 

Tire pressure is spot on, and I'd use the air filter as a dinner plate. Haven't checked the sensor though, so I'll give that a try - thanks.

 

I usually just manually check mpg as it seems like the mpg readers are never very accurate. I honestly didn't realize this truck had one - it's just showing time and temp, and I hadn't tried to see if it displayed anything else. I'll check it out tomorrow, but if it's at all accurate, it'll just be depressing!

 

I have a 15 4.6L DC 4x2 and get (running 75-80 MPH) 15 MPG highway and 16-17 MPG in town with a light foot . I have seen 19,5MPG on a country highway (no cruse control)
The cruse control is the worst it hammers the throttle to get back to speed .

 

when my '14 4.6L DC 4x4 was new I got low 16's mixed use.

after the ecu learned my driving habits I'm consistently in the high 18's driving in Seattle traffic.(which sucks)

road trips I'm at 20+

tire pressure (I run 40psi) & non top-tier gas affects my mileage as well.

give it some time... don't base your results on 1st tank.

 

are 255/70 a stock tire size for a 2011?

mine are 275/65/18... might make a difference?

 

+1, reset your ECU, probably still using shift points based on the old owners driving habits.

**Edit, I see you did, that could be part of it to then. Mileage is usually pretty bad when it's in that learning stage.

 

255/70/18 is the common base model tire size, even for the 4wd versions. 275/65/18 measures out at basically the same 32" height, but the 275 adds about 3/4" to the width. I just learned from the guys at Discount Tire that the 255/70/18 size is much more common in the tire world, and therefore noticeably less expensive. Example: I almost bought 275/65/18 Blizzak's, then realized the 255/70/18 version was $34 less per tire. The slightly skinnier tire will also be better in the snow, so it was a double-bonus to change the order.

 

I have a 4.6L, but 2WD, and I get half decent MPG. 13.8 sounds low. I would stop stomping on the gas, run some fuel system cleaner, and use cruise control as much as possible and see where you end up.

 

after the ecu learned my driving habits I'm consistently in the high 18's driving in Seattle traffic.(which sucks)

road trips I'm at 20+

tire pressure (I run 40psi) & non top-tier gas affects my mileage as well.

give it some time... don't base your results on 1st tank.[/QUOTE]

What you're getting is even slightly better than what I was expecting, and what my buddy says he gets. Thanks, I'll see what happens. I also just remembered that the truck has new pads and maybe new rotors in the rear, and am wondering if they didn't reseat the pistons correctly. Might be some brake drag...

 

Cleaned the throttle body and MAS today. Definitely looked like the throttle body needed some love, hard to tell if the MAS was dirty or not, but figured it wouldn’t hurt to do. It seems to be idling a touch high now, but throttle response is noticeably quicker.

 

I thought I remembered reading that when you mess with the throttlebody you need to do some type of relearn procedure. Hopefully someone will chime in. Or Google it and add tundras.com at the end of your search question.

 

Thanks man, that's news to me so I'll see if I can find something.

 

Give it a few tanks before stressing out.

 

Just found Nor7's writeup and he says "The truck will eventually re-program Throttle Body position but for more instant effect, remove battery cable to let computer reset." A few other online blurbs essentially say the same thing about Tundras, so I think it's fine.

 

Then after a few tanks, don't stress out either and enjoy it

 

Ok, seems like cleaning the throttle body has really changed the way it's driving - crisper throttle action, and it's not shifting nearly as rough as it was before cleaning it. Let me know if the above photos look like normal gunk for 80k or not, but I'm thinking that the previous owner let this truck idle quite a bit as it has a remote start, block heater plug-in, and spent most of its life in Alaska. Armchair mechanic'ing for sure with this theory, but I'm thinking excessive idling along with babying the truck has resulted in carbon buildup throughout the system, which may be the reason it's getting such sh!tty gas mileage. Any suggestions on other areas I should service? New plugs? Injector cleaner or service?

 

Yeah...but Denver is 5280 ft. Don't mention when going to the mountains here...Twice as high on a country road up there. Que in John Denver right about now.."Country Roads..Take me home....."

 

when I drive south toward New Orleans or the beach I can get 18-19 MPG . When I go north in the hills of N Mississippi its 15 MPG . 5000+ ft will kill your MPG and winter fuel mix wont help.Cheers

 

Changed the plugs today. Anyone good at spark plug diagnostics? My amateur eye thinks it was a good call not to wait for another 40k to swap them out at the suggested 120k, but I’m curious if these just look like normal wear or not.

 

Yum...fresh crawdads...

 

They ain't look too bad. Little Browning on the insulator. Never hurts to change them early though.

 

I agree too. I think I'll go with those OEM plugs at some point. I've got 83.3K miles now at 10 years old. Might be time to do the same and see how they look. "303z, I'm curious if your mpg will improve. Even a little is good."

 

The spark plugs show only a change in mileage if they're really bad, but it's good prevention for unburnt fuel. Having a clean burn certainly helps in the overall longevity of the vehicle.

 

One thing you don't want is even one plug totally fouled up for sure. The onboard computer does a great job of keeping the fuel/air mixture ratio up to snuff.

 

Thanks for the thoughts on the plugs, guys. After swapping those out, cleaning the throttle body, and running Sea Foam through a vacuum line, I ended up with 17.6mpg with a bit more city driving and more mountainous highway driving. Hard to say what did the most good, but happy it made a difference, regardless.

 

'13 4x4 dbl cab with 4.6L. Purchased used with 30k on the clock. First tank was a road trip and I manually calculated just over 20mpg. Unfortunately it's been down hill from there. Through the fall with mixed city and highway driving I got between 17 and 18. Now with the cold weather it has dropped below 17. That could be because here in SE Wisconsin they mix 10% butane with the gas between October and May.

 

Mine is a 2012/4.6L DC with 48400 miles. I average 14.5-15.9 on the dash estimator running 87 grade. This is on 50/50 city/highway.