Nothing you've listed, individually, would drop his economy 3MPG on highway runs.

Combined is a different story.

PS: You can rule out "mods" as he clearly stated in the opening thread that he has none.

 

that is what i cant figure out... temp +5- deg., tire pres. same, roads same, time idleing +5min.-, mods same. driving conditions same, driving habits same. everything is the same. i am going to start throwing parts at it and see what i can come up with. but any suggestions would be great.

 

I'm gonna throw this out there and maybe you can explore it further if you so please.

Maybe your truck's MPG readout is faulty?

Three MPG drop out of nowhere is quite significant.

But, like many have touched on, it could be a number of things.... but my guess is a couple of things combined.

Get Ford to check your MPG readout.

 

i thought about that, but kinda blew it off. i will have them check it out. im not so much woried about my economy as much as i am that it may be a precursor to something else. thanks for your help.

 

Good luck and please keep us informed.

 

I'm going to throw this out there because nobody else has yet. It seems you're on top of things maintenance wise, but what about weatherman wise

Wind direction on the highway makes a HUGE difference. I've had many different results in mileage driving the same long route. I didn't actually hand calculate them but, I always reset the trip odometer everytime I fill the tank before leaving, and I know what I generally get before that needle hits the 3/4 tank mark. It can change around quite a bit depending on wind.

 

don't know if this applies, but in Ontario most of the pumps now say they "may contain up to 10% ethanol" which means sometimes you might get 1 % other times you might get 10 %. We used to only have one supplier (i think it was Suncor that supplied Sunoco and UPI stations) that had up to 10 % and i noticed significant decrease in my mileage when i filled up there.

 

good point. i dont know if that is why it fell so fast, but at the same time it was a round trip. i know that going down it was very windy, but coming back not so much. but i can deffinately see what you are saying.

 

If you had some way to monitor your TPS you could check this wind thing - log TPS at steady-state cruise in both directions.

Know anyone with a Scangauge or Dashhawk?

(BTW - anyone know if the cluster diags show this parameter?)....

Just sayin' ...

 

Im noticing less mileage per tank but that always happens at this time of year.

 

Isn't it a little too soon for winter blend gas up here?

 

I would think so but this happen to me the last 2 years at this time. When is the winter blend suppose to come out?

 

Sounds like a good idea but what if the wind changes direction on the trip back?

Just sayin'..

 

You are definitely due plugs, MAF cleaning etc., at 90,000. But, have you changed tire size?

 

naw, stock wheels and tires.

do the 04+ have the same plug issues as the 97-03? i heard that they put "more" and "deeper" threads in the heads, but people have had problems with plugs breaking.

in another thread i asked about plug and COP recommendations. opinions?