I just bought a new to me truck. It is a 2002 F250 CCSB v10 4wd with 3.73. So far I have gotton 9.2,10.1, and 10.2 mpg with it. The truck seems to be all original no mods to it. I also have a 99f350 CCLB 4wd V10 with 3.73 gears. The truck seems to get a cosistant 13 and it get 8.5-9.5 pulling our 8000 pound horse trailer. The truck has a cone style air filter thst was on it whaen I bought it along with the cat being removed and a aftermarket muffler. Whay does this truck do so much better on mileage than the 2002? The 99 also seems to have more power, maybe not as smooth as the 02 but more throttle response.

 

It appears like the exhaust mods are giving you more mpg?

 

Your 2002 v-10 should do better than 9.5-10 mpg . Obviously you have another V-10 truck and you are not a stranger to V-10 . My 2003 gets 13.5-14 mpg on straight hwy drive , despite 4.3 rear end ( I drive 60-65 mph with imaginary raw egg under the gas pedal)

If it were mine I would do the most obvious DIY items first:
-Clean MAF sensor
-Change Air Filter
-Change Fuel Filter
-Change spark plugs and rubber boots

Good luck,

 

FWIW

My 2003 is getting a fairly consistent 10.5mpg empty, mixed driving, with the 10% crap-anol laced gasoline. There's a couple of stations near me that sell 100% petro gasoline and I've been meaning to run a few tanks of that stuff thru it. But I drive my truck so seldom that I just haven't gotten around to it.

I think I would literally do cartwheels if I could get my empty mixed driving mileage up to ~12mpg.

 

Could need a tune up.. Possibly a dirty MAF, or a bad PCV valve.. I was having the same problem with my F250, turned out to be the PCV valve and mileage went back to normal which is about 13-13.5

 

Pardon my ignorance, but is the PCV valve the one located on the passenger side valve cover?

 

Yes, on the top of the passenger side valve cover. Very cheap and simple fix

 

I'm trying to process this. How would a faulty PCV valve cause a 2-3mpg drop in fuel mileage? Clearly I'm not an expert on this subject.

 

I am not an expert either, but if it is plugged it could result in a mpg decrease because it the engine isn't getting enough air therefore running too rich, if it is stuck open it could cause the engine to have a lean air/fuel mixture. It can also allow cause excess crank case fumes to be sucked into the induction system, affecting combustion and fuel mileage.

 

Along with that, higher than normal crankcase pressure can "push" oil out, past gaskets, rings etc. Found that out on a intake manifold change as a lad, pre internet

 

Now, THIS makes total sense. I can definitely see how excessive, un-vented crankcase pressure can cause issues. Especially in the long-term.

 

Ok I think I am going to change the plugs(scared!) new boots,PVC valve, clean the MAF, and maybe dump the cat and put a new muffler on it(not sure on this last item yet). Which plugs should I use and any tips in regards to changing them. Also thinking of going with a tune from 5star down the road too. I have also been noticing what seems like a bit of a miss sometimes at 45-50 mph. Any thoughts

 

I know the 99 has a lot more power than the 2002, anyone have a guess as to why that is?

 

There is a thread on here about replacing plugs. I prefer motorcraft parts for everything I replace. Check out SPD performance or 5star tuning for a ypipe before changing the rest of the exhaust system. These are known to be restrictive. If you are having a noticible miss you may want to plug a scan tool in and see if there are any codes otherwise a couple new coil packs may help but that could take a while to figure out which cylinder needs the COP.

If your 99 has more power than something is wrong with the 2002. Tune up is the best place to start. Might as well change the fuel filter while your at it.

 

I was always told that the 2 V 6.8's do real well with a new Y pipe and aftermarket muffler. Also delete the resinator. Along with the tuneup, you should notice a big difference in power and mileage.