mooseman

I filled up today and checked mpg. I average 19 mpg with normal everyday driveing but at the last fill up I only averaged 10.5. Why? I actually drove with a softer foot on the last tank because of the ice on the roads. I did not idle more or run in 4x4 more than usual. I thought my average would be about the same or higher. Is there something that could be causeing this besides someone siphoning my diesel.

Thanks, Mooseman

Shovelhead

Local suppliers might have switched to "winter" formula fuel already.
Less BTU = less MPG.
Also might be taking longer to get the engine warmed up to its peak efficient temperature.

I usually lose 1-2 MPG during the winter.

Haulin_in_Dixie

You might of just gotten a bad load of fuel, happens sometimes.

handymantim

9 mpg is a big difference. First thought was not-so-perfect math. Sorry, didn't know how to state it any other way.

Can you even siphon out of these trucks? My 94 Ford Explorer has a screen in the fill tube to prevent siphoning. One would think these more modern vehicles would be equally equipped.

Is it running any differently? If not, I'd wait for the next fillup and see how that tank went.

IntakeRacing

lol a guy at work had that problem with his ford... kid next door would siphon a bunch of gas every night or so untill one day he took 3/4 of his tank. hahhahaha.. ran outa gas on his way to work!!! he didn't even look at his needle... oh man was it priceless


but on topic i noticed a big mpg drop come winter..

phox_mulder

Mine had dropped from 16mpg average to 10-11.

Also noticed my fuel pressure had dropped from 15 to 14 at idle, and 13ish cruising to 11ish.
WOT wouldn't go below 10 though, thats a good thing.

I changed the filter last weekend, thinking that might be part of the low FP problem and noticed Diesel dripping from the bottom of the filter can.
Never saw any evidence on the driveway though, don't know how long it had been leaking.

I guess everything plumbed in for my FP guage had vibrated loose.
Tightened everything up and took a long drive (Idaho, powerball tickets).
Checked my mileage and it's up to 15 now, no more drip.

Check for leaks, check the filter, check for smoky next door neighbors cars,
(siphoning your Diesel for their gassers)
or chalk it up to a very bad load of fuel.


phox

Kyle Graham

That seems pretty harsh even for winter fuel I'd look for a fuel leak

mooseman

Thanks guys for the advise. I have already checked my math . I have not noticed any leaks on the garage floor so ill pop the hood and look real good. If nothing comes from that ill just wait until I fill up again. That tank of fuel was from a different source because my usual pumper was closed when we decided to go on a road trip. Maybe its back to the funny red fuel, it sure seemed to be more consistant.

Thanks, mooseman

Hey Phox next time on the way to I DA HO stop and jump in with me. I run that way every chance I get. One day it will pay off

dodgediesel4x4

If you get the same results with from the next fill up, then you might try an APPS reset or try cleaning your IAT sensor. Would do nothing but help. Just a thought.

Charlie Hardin

Can you even siphon out of these trucks? My 94 Ford Explorer has a screen in the fill tube to prevent siphoning. One would think these more modern vehicles would be equally equipped.

You bet you can siphon a 98 12 v. One night at one of those multi-grade pumps I had a massive dumb attack and inadvertently pumped 24 gallons of 91 octane gasoline into my baby! Pushed it off to the corner of the station, hitched a ride 20 miles home for all the gas cans I could find and spent the next 1 1/2 hours in a rainstorm sucking the mix out of that truck. Cost me almost 100 bucks for fuel that night! Thank goodness the only harm was to pride and pocketbook.

iker42

Have you covered your radiator? I lost 3mg because of the temp and the cummins method of pre heating, once i put and cover in i got back about 2.5mpg.

mooseman

I filled up again today and my mpg is back up to 18.5. Ive been asking around locally and everyone that has bought diesel at smiths fuel center has noticed bad mpg and poor performance. I will not be filling up there again ever.

Thanks, mooseman