darrenG

In the past 2k miles I've replaced the ff, air filter, crank position sensor, vp44 and lp. Late last week I changed my oil and filter - used fleet guard #correctnumberformytruck and Rotella. Since about the oil change my mileage dropped to 13mpg city from 18-19. It's not leaking diesel that I can find / smell, the performance is just fine, oil pressure and fuel pressure are normal. I know they do something to the fuel for winter that curtails mileage but it's a little early. No codes that I know of, either. Any ideas?

CTD NUT

Have you actually checked for DTC's? I would re check if you haven't......do the APPS reset and clean the IAT sensor for starters.

j-fox

Suspect that IAT sensor.I bet it is out of range, but not a failure to set a code!!

darrenG

I was hoping bad diesel. One day it was getting 18-19 and the next 3 or 4 days I know the mileage cus I filled up and calc'd 18.9 and watched as the gauge started dropping like it was my 77 Power Wagon. I'll have to run the scan tool.

DarkPaladin

Does your station "premix" fuel for you or did you gget #1? Here in AK they premix it for the tems for use, No seperate pumps...

darrenG

I filled up at a station I usually do. I'm pretty sure they premix it for me.

high country

it will only take you 10 minutes to clean the iat sensor

toddbweaver

I have a friend who just bought 02, automatic 4.10's , with 25,000 miles, it's a 1ton regular cab 4x4 with a dump body. His first tank was 11.6 mpg's and he's not a happy camper. I'm getting 21-23 on my 04 and I told him he should be getting close to 20 unloaded. What is the best way to figure out why his mileage is so bad?

Mopar1973man

While your there pull the MAP sensor too and clean it... It can get gummy inside.. Improved my MPG numbers... But IAT sensor is a dead give away for cleaning.

Just my 2 cents...

Lary Ellis (Top)

Winter blend fuel, it gets us all this time of year.

P.J

Could it be that bad though? I remember dropping down to about 15-15.5 (v.s 17-18 summer).

13MPG seems a bit much.

RowJ

Agree...Not that bad!

AND #1 diesel fuel in September??? (when he first noticed the problem)....I don't think so! Does not give his exact location so maybe - I know the Mason Dixon line does not switch over to a light blend of #1 until OCT.

RJ

darrenG

Kalamazoo, Michigan.

I think it may have just been bad diesel, cus the mileage went up and I got around 15 towing my toyota.

Watching that gauge plummet made me panic. It reminded me of my 77 Power Wagon (8-13mpg), I got sker'd.

TORQUE

Clean both IAT and MAP sensors first, check resistance on both to see if they are within specs and reset APPS. You will lose mileage with a blended winter fuel, it all depends on how they mix the proportion of #1 in with #2, or could be just straight #1, each refinery varies from brand, and location. You would have to get info from dealer if he even knows


Did you check for codes, I see you c/o VP-44 did you/they use same key for base timing when installing pump, this will affect power and mileage if timing is too retarded?


Your mileage shouldn't drop by more than a couple mpg running with #1 as compared to #2 summer diesel. Have you got a boost leak or notice more smoke, this will cause poor mileage, as will dirty injectors. Add a double dose of injector cleaner for a few tanks. Keep track of mileage after doing/checking all these things.

MCummings

WAYYY Different trucks.

Automatic
4.10's
Dual Rear Wheels
Long Bed
Dump Body

His truck is never unloaded.
However,, Your truck,,

6-speed
3.73's
Single Rear Wheels
Short Bed
Factory Bed...

Your truck should get almost 20 at 65-70, compared to his should get 13-15 at 65MPH.


Check your fuel pressure. A drop in fuel pressure will definatly hinder the injection pump's ability to pump fuel, resulting in lower MPG, and power.

Merrick