Fuel lossb

[02 Duramax]

I have a 2002 Chevrolet 2500 Duramax ext cab 4x4 with 155,000 mi. 265/75R16 BF Goodrich tires. Had been consistently getting 17mpg, occassionally 18-21. Seemed like overnight, it dropped to 15mpg for about a month, then 13 for a couple of weeks. I changed the oil and drained out almost 7 gallons. Since then, the oil level seems steady at normal.
I took it to my mechanic who changed the fuel filter but suggested I go to the dealership to have them test the injectors. Since the fuel filter change, I have to prime it to get started, then runs fine. I took it to the dealership, but after testing it, they said the injector were fine and there was no diesel in the oil.

The last 3 consecutive fill-up's since then, I have gotten 11mpg. No one seems to know what is causing this. Can anyone give me any insight?

Thanks,

[gfd464]

Its called Ultra low sulfer diesel, I have the same problem, and everyone I talk to has it ever since they made the switch as of the 1st of the year!!!!

[mbmax]

The original sympton sure sounds like classic LB7 injector troubles. Maybe try another dealer.Somebody with more knwledge might help out here but apparently it takes some time to properly evaluate. I think your mechanic who changed your fuel filter has intrduced an air leak. Maybe o ring on filter not sealing and also check around filter for fuel leaks wher it mounts up and check bleeder screw for tightness. I hope this helps. Good luck!

[mbmax]

Also , withdue respect to gfd464 ulsd fuel will not reduce your mileage by that much nor will winter blend fuel.

[Kennedy]

Also , withdue respect to gfd464 ulsd fuel will not reduce your mileage by that much nor will winter blend fuel.

Agreed

Winter driving conditions, low temps and such will. Additize your fuel also helps.

Sounds like injector issues. The need for bleeding sounds like the leaking is severe enough to hamper proper pressure during cranking.

[Buck]

FYI, I've run USLD in my 2005 Dmax and mileage didn't change at all.

[Mark Rinker]

You drained out HOW MUCH at your oil change??? Did you really mean 7 gallons??? 7 quarts is way low...???

[DmaxMaverick]

If you drained 7 gallons from your crankcase, you have a serious issue with return lines or injectors. A cracked or loose return line will dump fuel into the crankcase at a much higher rate than a failed injector. Been there, done that. If your problem is intermittent, I'd suspect injector(s). Keep a close eye on your oil level. If you see fuel in the oil again, the dealer should take care of it. You may not see fuel in the oil immediately after a change, and it may require certain conditions to cause the leak. Like long highway runs or towing heavy. Your leak may only be occuring at higher rail pressures.

[carco]

FWIW we have all been on low sulphur fuel to one degree or another since Oct. 2006, maybe as early as July, 06. bob.............

[02 Duramax]

You drained out HOW MUCH at your oil change??? Did you really mean 7 gallons??? 7 quarts is way low...???


Yes, I drained 7 "gallons" of fluid, out of the oil pan, that was thin as water and completely black.
I now have close to 1,000 miles since the oil change and the oil level appears to be about 5 times the full level and is looking black and thin. Also smells like diesel.

[02 Duramax]

Just wanted to tell everyone that I appreciate your thoughts and advice. You have been very helpful.

Thanks,

Alan