I just filled up for the third time and I hand calculated that I am getting 9.27 mpg city and highway combined with no idling at all, is that really low? Is something wrong? I drive like theres an egg under the gas pedal and coast to all stop signs well in advance, thoughts? I have 195,000 miles on the rig, all stock except for K&N air intake. I was thinking about replacing the O2 sensors and seeing if that improves it. Then I was going to do spark plugs. What do you guys think? And before I hear "its a v10 it gets bad mpg" low mpg can be a result of needing basic maintenance. I already cleaned the MAF, should I change the fuel filter? I also did synthetic fluid in the trans, diffs, and engine, thoughts? I am running a 5w30, so that could explain a slight drop in mpg.

 

Fuel filter is the next thing you should do, and of course plugs and boots. All stop and go, I got 5.5. A combo of stop and go, and highway on a normal commute to work, 22 miles on way, I got about 9.5. So you're right in the ballpark. But I wasn't easy on the go-pedal either

 

That sounds about right for combo driving, I only drive local and that's about right. Took a trip to Maine last August and got over 15 average for the 1700 total mile clocked.

 

geez man that seems awfully low. Is that your three tank average?
What kind of truck do you have?
oversize tires?

 

yes 3 tank average, 265/75/r16, and when i say city I really mean suburbs, which is like 45mph with stop signs here and there. And I dont let it idle more than 10 secconds when I get out.

 

Are those tires stock size?
What kind of truck is it?

your described driving habits seem normal.

 

its an f250 quad cab short bed, and yes stock, however they are all terrains, not very aggressive at all, just enough for snow plowing. Hubs arent locked and I never rev the engine up very high. What should the 02 sensors be? I have diagnostic tools at my disposal.

 

Man I could be wrong... but I don’t think that’s normal.
I have a v10 van and I get 11.5-13.5 all week every week. And I’m not nearly as strict as you described about idling.
granted I do a lot of highway driving so that helps my mpg figure.
When I tow my trailer (7,000lbs enclosed) it gets 7.5-8mpg.

I bet you got a brake dragging or something.

What about tire pressures? What’s the max ? And what do you run?
Does it have a snow plow on ? Anything else hurting aerodynamics? Like the rollover bar thing? Lift kit?
Are those tires the correct size?

 

no brakes dragging, there hasnt been a plow on it this season, running max psi in the tires, no lift, nothing after market like a bar

 

ok I’ll step out here and watch what everyone else says. Krewat definitely knows his stuff. I struggle to believe his claim of 5.5mpg but I do have faith in his knowledge and experience. It’s just that 5.5 is drastic.

And mine gets a few hundred highway miles on every single tank so maybe my judgment is skewed more than I know.

The thing is- I’ve done the fuel economy game- when I put lots of effort into maximizing MPG, I can squeak out low 14’s. When I drive like normal, and in the summer with a few hours of idling time (for a/c usage) I get low 11’s, and an occasional 10.xx.

and of course towing- my van with 7,000lbs enclosed trailer gets 8mpg. That’s comparable to your truck without a trailer.

Ok ok anyway I’m out.

 

My 06 averages 9.5 to 10 mpg with similar driving as the OP. Country roads at 50 mph and in town driving. I rarely get into the throttle hard. The throttle body has been cleaned and next will be the MAF and new plugs. 90k miles and it's unknown what the other owner did to it for maintenance. I think my bigger issue tire size vs. the OP and I've accepted that. It does seem to go down with the added weight of the canopy on the truck which seems somewhat counter intuitive as the cap should also improve aerodynamics a bit (if there is such a thing with one of these trucks).

I would be happy with 13 for highway driving. 9.5mph is a little disappointing but I'm getting used to it.

 

Bought my 2001 F-250 V--10 new. Before I lifted the truck 4", I would get 11-13 highway, 10-12 mixed driving out west around southern AZ. Lifted my truck and I now run LT315-75-15s. Speedometer is now 10% slow, so when I figure my MPG I have to add 10% of whatever is shown on trip odometer. With 3.73, I would get 10-12 highway, but towing or hills, truck seemed to struggle, and I may get 10. I re-geared to 4.56, and now truck does not struggle. Towing my 20ft cargo trailer loaded, 8-10k lbs., I got 7-10 mpg, depending on wind and terrain, driving cross country twice (AZ to southern GA). Mixed driving here in GA I get 8-10 depending on how hard I drive. I don't burn rubber on launch, but I don't baby it either. Highway I get 10-12 driving 65-70, drops to about 9-10 running 75. Towing my 18ft boat, 2 axle trailer, truck doesn't seem to even care that it's there.

 

IF it's on flat land it is a bit low. If it is hilly it probably is normal.
Check the following things;
-hook up a scanner and see if long term fuel trims are not out of whack ( close to 0 is best, under 10 or above -10 is ok)
-Check the slide pins on the brakes. Remove them, clean them, use some brake grease and re-install. Does the vehicle brake ok ? Any pull to the left or right when braking?
-alignment ok ?
-smooth idle?

Also, you said you drive very relaxed. What speeds do you drive ? The higher the more fuel it uses. It makes a big difference. Stop and go is murder on mileage with these tanks.

Forget the fuel filter. It won't reduce your mileage if it's clogged, it will just result in the engine running like crap.

 

just changed the pads on all 4 wheels, regreased the slides, i drive 65mph on the highway, and usually 45 on backroads. Ill hook up a scanner to see what it says, alignment was just done and brakes work flawlessly.

 

Here's a near 6 year running record