JBOND

On my '05 we've been getting about 23 mpg since buying it new. It's got 83,000 and all the sudden the last month the mileage has dropped to 15-16mpg. Put some injector cleaner in------what in the world could make this happen?

Spooler

How are you determining fuel mileage? Calculating by hand or the overhead? You may be starting to have an injector issue and using more fuel.

zulusafari

if you had dealer service work, did they re-flash the computer? I have read several accounts of people's mileage dropping following a software reflash -- most stated it lowered the overhead value closer to their hand calculated though, not really the performance.

1985cucv

winter fuel

rockcrawler304

Check your oil level!!

Raspy

Maybe you just stopped driving it downhill with a tail wind. 23 average is very high for an '05.

Steve-l

I don't believe 23, unless you have driven 83k in a vacuum. 15 to 17 mpg is normal for city driving and NOT towing.

rammer123

My mileage drops with winter fuel

Lost Lake

Sounds like a fuel leak or a leaking injector. Check the oil level for fuel, watch for black smoke, and look for fuel leaking down the engine or from the tank.

From what I've heard, excess fuel in the cylinder is a short path to a rebuild...

trksrfun

23 seems a little high for that year but it does not seem to far fetched... Mexico is a flat state so there is no big hills or anything like that that would lower fuel mileage, as well as if the driver was driving like an old man on a sunday cruise all the time....

like others have stated check the oil for color, see if its darker then usual as well as exhaust for black smoke. Do you have an EGT gauge? if so do temps seem slightly higher then usual?

my thought is that its the winter fuel more then anything.. good luck with finding it out.

JBOND

Thanks for all the advice. 23 is while NOT towing----it does drop as would be expected when towing---but this is not my towing vehicle it is the wife's going to town for groceries rig. So no big over sized eat the fuel mud slinger's on it! Haven't had any dealer service done, but will be sure to check the oil for fuel. Did an oil change about 300 miles ago though and didn't see or smell anything unusual. It has gone up some since running the injector cleaners.

Raspy

The problem is definitely not fuel in the oil.

Look for something else or hand calculate more accurately. You are hand calculating, aren't you?

JBOND

I watch the overhead just to get an idea but I hand calculate regularly.

Grit Dog

Maybe your wife's drag racing the local boys when she goes to town!
If the truck hasn't been reflashed, maint is kept up, and no fuel in the oil, I dunno. Winter fuel is only going to drop 1-2mpg tops and you probably don't have a real stiff blend yet in NM.
Brake hanging up. Stuck in 4wd and don't know it. Usually most mileage problems are injector related. Maybe have the balance rates and return rates checked.