Poor fuel mileage

[2000SuperStroker]

My truck used to make about 18mpg in early spring and dropped to about 15mpg all summer long. It has new fuel filters on and I am pretty sure the fuel is good another truck is making about 20mpg. It seems to crank a liitle longer then it used to and it takes longer when the oil is warm. It might have a little loss in power but not a lot. It does have 222000 on it, could it be the ICP, IPR, or the high pressure oil pump.
Thanks Gail

 

[CHPMustang]

With my experience of the new 15PPM fuel it could be the quality of the fuel as our 7.3L exhibited the similar symptoms till I changed PPM level fuel or went to a BioDiesel blend which helped alot.
Have you attempted to add products like Lucas Oil Fuel Treatment or Stanadyne Fuel additive to the fuel as those two will add the needed lubricity to the 7.3L.

How many miles on your oil?

Run a Blackstone lately?

Here's a Thread I started pertaining to recent fuel quality/engine performance that'll be worth a gander

 

[JLDickmon]

I agree.
S15 S-U-C-K-S for use in the 7.3...

you could locate a B20 pump (which I did) or tip in a qt of TCW3 two-stroke oil on each empty tank to restore the lost lubricity...

might want to look at this thread, too... POKE

 

[2000SuperStroker]

I pour in about 4oz of marvel mystery oil for every 10gal of diesel. Less then 2000 miles on a change of Shell 5w-40 synthetic, the pour milage didn't start with the oil. I get my fuel from a 1000 gal tank of road fuel at home here, it has 2% bio in it. I haven't seen any B20 pumps around here. LSD is almost impossible to find also. On the same fuel my dad's '95 f350 five speed is making the low 20's.