Hello
I have a 2002 F350 v10. I have had it for around 2 years now. I love the truck but have been experiencing horrible gas mileage recently. I have went from 10-12 miles per gallon to now 5. I do have the SCT TUNER from Mike at 5 star. I do have a 12" lift and a cold air intake with 4" dual exhaust. I have 105,000 mile on it. The truck is not running rough or missing at any speed. I have ran the seafoam through it like Mime had suggested. It is not my daily driver and I don't expect 15-18 miles per gallon. I would just like to get my 10-12 miles back again. Looking for help.

Thanks

 

Did you do the plugs at 100? How about fuel filter and PCV valve? Have you cleaned the MAF sensor?

From the PCV valve on the valve cover there is a hose connecting to the bottom of the throttle body that is known for cracking which will make your truck burn more fuel. I would check that out.

 

Save perhaps those of the Intake & Exhaust ~ The "Mods" You've listed do NOTHING to "Improve" Fuel Economy...but 5 mpg does suck!

Think of those reasons the PCM feels You're requireing MORE FUEL to Run...otherwise:

The MAF (Manifold Absolute Pressure Sensor) out-of-range - seeing MORE Air than "real"?

O2 Sensor(s) "Biased Lean"?

 

Yes I have changed the plugs and the wires. I have not done or looked at the PCV Valve or the MAF. I will check those out And replace it even if it they don't seem bad. They are cheap and it can't hurt to just do it.

If the fuel filter was bad wouldn't it be like cutting out if I had it under load or driving up hills? I have no problems with it at all.

6 months ago I did replace my computer. This was because my odometer/cluster had stopped working. I was wondering if that could have had something to do with it.

 

no free lunch on tuners....either they increase power and run your fuel ratio richer tanking your MPG or they increase economy by leaning the fuel ratio at the cost of hotter temps.


a rich mixture could clog the cats with carbon build up...plausible explination for a sudden drop in economy. how does your operating temp look? and rotten egg smells?

 

I have taken the tune completely out and driven over 200 miles and still have the same 5-6 miles per gallon. Operating temp never moves stays the same. Trans temp never moves even when I'm pulling my toy hauler. I have not noticed any kind of rotten egg smell.

 

https://www.ford-trucks.com/forums/1...ml#post9993705

I drove through a huge muddy water puddle once. 5mpg after that until I cleaned the MAF and throttle body.

 

So you used over 35 gallons of fuel to drive 200miles?

Any chance someone is thieving it from you?
And obviously a fuel leak would have been noticed by now...

If it's not being misplaced in liquid form, as above, then it must be getting burned. If that quantity of fuel is being burned, but the results of the work are so terribly reduced: then you should be able to track down the wasted energy in the form of heat. Dragging brakes or drivetrain would add heat to the corresponding parts/fluid.

Also what about throttle "feel"? Does it have a lack of its prior-known thrust?

Keep us posted- this is a good mystery.

 

I'd pull one or two plugs to check their condition. A too rich condition should readily present itself which would at least be a starting point for further diagnosis to begin.

 

I am not loosing the gas to someone and I have no leaks. I have now changed the fuel filter and PCV valve. I have got the millage up to 7.8 now by doing that. I have not changed the MAF sensor yet. Will do that this weekend. I have also pulled a couple plugs and they look brand new. They only have about a couple thousand mile on them now. This is not my daily driver but I would like that 9-10 mile range around town again. Please keep all ideas coming as I am taking the truck in today for a front end alignment. I was told that if it not perfect it will cause a drop also do to friction??

 

No need to change the MAF, just clean it first. Super easy procedure - get her done!

 

2mpg from changing the fuel filter and PCV is a great step forward.

Definately clean the MAF. It will help. This is the stuff I have used. Works great.


What kind of intake do you have? Has the filter been cleaned?

 

I ordered the cleaner you have suggested. I will clean masair this weekend. I also have discovered that both front hubs are now in need of replacement. So I have ordered the hubs and will replace those this weekend as well. That should help a little on cutting down on the drag. Thanks for all the input and keep them coming.

 

^ Wow, if your hubs have been locked the whole time that will definately kill the mileage. I would also lube the slide pins on the calipers with some grease and shoot some into the wheel bearings if you have a grease gun.