Hey all,
I recently bought a 2003 Ford excursion with a v10 (I new gas mileage wouldn't be amazing). But judging from other posters I've seen, I feel that I'm below average and I can't figure out why. I'm only averaging 7-8 mpg mixed driving by hand calculations. Oil changes have always been on time and the oil was just changed, engine seems to run perfectly and there's no lights on the dash. 80psi max tires are filled to 65psi. I'm not hard on the gas or brakes. Is there anything you guys could think of that would be a potential issue or any tips you'd have to get a small improvement out of the truck? Even getting to 11-12 mixed would be awesome

Thanks,
Shane

 

Welcome to the EX forum Shane!
That does seem a little bit low for mixed driving with easy on both pedals.
Do the brakes pull to one side or the other when applied? Or even when not applied? A dragging brake pad can provide enough friction to rob some MPGs. Feel your wheels after a good drive, do any feel hotter than the others? The brake caliper slide pins are known to get gunked up and not slide as intended which will have a brake pad dragging. Disassembly and cleaning then relubrication of the guilty slide pin should fix that issue.
Is the front end alignment good? Are the tires wearing evenly? A bad alignment can be another MPG killer.
How many miles on the engine? Higher mile rigs may be seeing dirty, fouled, worn out or damaged O2 sensors. Your V-10 will have two primary sensors in the exhaust down pipes just after the exhaust manifolds and a third one after the cat if its a California spec build. The first two are the ones that give feedback to the engine computer to adjust the rich/lean mix, so if one or both are going bad it can be running too rich which will drop the MPGs. Recently we had a member who's O2 sensors got wet during a head gasket change and his mileage dropped by like 4 MPG, a fresh set of sensors brought his mileage back up to a little better than before the gasket job.
You mention the tire pressure, but their size. Any tire taller than the stock 265/75R16 (31.6" tall) throw off your mileage calculations. For an example my 35"s are 12% larger than the stocker so when I do my MPG calcs I have to add that 12% to the results. So if my calcs show 10 MPG it's actually 11.2 MPG due to the bigger tires.
Do you when the spark plugs were last (or ever) changed? If you have worn high mile plugs and the rubber boots that cover them, changing out with fresh plugs and boots should help with your mileage some and provide smoother and crisper running and acceleration.

 

If everything else Tom has mentioned is good, do the O2 sensors. By changing them it's let getting new spark plugs in your engine. Cheap to do overall.

Most people don't realize the difference changing these can make. Do all of them.

 

That does sound a little low, good advice above.

 

Thanks guys, I will start going thru all these things one by one and try to document any improvements as I go. I'll update you along the way!

 

check your actual coolant temp via the OBD-2 port, your t-stat may be stuck open and never letting engibe warm up and as a result overfueling.
With a bkuetooth dongke and app, yiu can check fuel trim left vs right bank of cyclinders, and lots of other things to help find the culprit(s) ans check other thibgs as well.

 

Misky, did you type this with your toes?

 

Nah, he calls anything that's NOT a diesel an engibe. He was also playing donkey kong at the time too

 

I m txt n y'all

 

I think it may be the shivering from the cold weather

 

Personally those are the kind of numbers that I used to get mixed driving by my definition.

Driving around town mostly and a quick highway run here and there I'd be lucky to see 9mpg.

Highway mileage I used to get 13.5-14 mpg like clockwork

 

That's the thing, everyone has somewhat different mixes and realities of just what "city" and "highway" are in their usage. Part of my daily driving is within the city of Philadelphia, an old tight (not built for cars) congested place for sure, but the section that I drive is on the outer industrial/commercial zone where the lights are fewer and the 4 lane roads are 45 MPH that actually stay flowing. If I had to go into Center City or worse the Old Town section it would be a 5 MPH crawl on cobblestones with lights every couple hundred feet and gridlock during rush hours. That would definitely have a different MPG result than the "city" driving I have to do. My local "Town" driving is mostly on our old twisty hilly narrow (founded in 1686, not built for cars either) roads with only a few lights, a different scenario than what others may have with wide open flat suburban sprawl. There really is no "typical".