I have experience with the smaller modular motors like the 4.6 and 5.4 triton. The gas mileage i have no clue on but at one time ford was going to shoehorn the 6.8 V-10 into the P71 interceptor 
I had the 6.8 V10 in a 2001 F250 SD extended cab 4x4 with the manual tranny; I got 13-14 mpg on average. That's why I ditched it, as nice a vehicle as it was otherwise.
I have a '99 extended cab, 4x4. long bed, manual transmission. As Perplexed mentioned, 13 to 14 mpg. That maybe with the wind and downhill. The spark plugs can be a problem. Only a few aluminum threads to screw a steel spark plug into. I bought my truck used and the previous owner (unbeknownst to me) had already had a few of the spark plugs "blow out" and had steel inserts installed to repair the holes in the head. Well, at least one of the repairs wasn't done correctly and the steel insert blew out. So a standard repair could not be performed. Had to pull the cylinder head and have it welded. Nasty and expensive job. Not sure how common a problem that is. That's just my experience.
Have the front end checked out - replacing the ball joints is quite a job and is very expensive if you have a shop do it.
Have the front end checked out - replacing the ball joints is quite a job and is very expensive if you have a shop do it.
I Have a 2005 Excursion with the 6.8 V-10. I run Royal Purple synthetic keep it at 68 on the highway and average 16.2 Hwy and 13 in the city. The truck has 131k on it. This is my second Ex with the same motor (first one was a 2002). Same gas mileage, I traded off the 2002 because 05 was the last year Ford made the Ex.
Have never had a problem with plugs blowing out. If you change them just make sure you don't strip the threads.
LRP
Have never had a problem with plugs blowing out. If you change them just make sure you don't strip the threads.
LRP
Co-worker has the v-10. He has had trouble with the plugs but it was a used truck when he got it...not sure if the first person did the job right or not the first time. Had to put in a steel insert in one cylinder. He has also had trouble with the plug wires....coil on each wire....seem to be a bit fragile. He has had a couple of them crack. Keeps an extra with him.
He's never told me what type of MPG he gets other that to say it is not great. I remind him it IS a v-10. He smiles and goes on his way.
He's never told me what type of MPG he gets other that to say it is not great. I remind him it IS a v-10. He smiles and goes on his way.
Not my experience, but a friend has a mid thousands 250 Super Duty used to deliver oilfield equipment (BOP stuff, which gets really, really heavy) and has had no problems at all out of his V-10, over 200,000 miles now...factory trans and motor, but I couldn't tell you whether this is the majority or the minority, I would check edmunds.com for writer and consumer reviews...
Edit: expect tops 17 mpg highway probably 15 more than likely and 10-11 in the city...
Edit: expect tops 17 mpg highway probably 15 more than likely and 10-11 in the city...
My 2000 model 5.4 got 19 mpg. My buddy has a V-10 and the only problem he allows is the 13 mpg he gets.
Here's a link on the Ford-Trucks forum from last year on the longevity of the 6.8 V-10.
http://www.ford-trucks.com/forums/1003553-v10-durability-and-longevity.html
LRP
http://www.ford-trucks.com/forums/1003553-v10-durability-and-longevity.html
LRP
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