I Know my truck is a 1999 and has 196,000 miles but I've been getting 24/26 MPG for a long time but in the last couple of months its gone to 19/20 MPG and wanted to check on line before going to a dealer. Does anyone have an idea why the change in MPG??

Thanks

 

The dealer will tell you that as much as it's supost to get. But you might change your air and fuel filters. I've heard a weak IP can couse low MPG's also.

 

I also heard winter fuel does not get as good MPG.

 

I'm new to the cummins 24v but I have seen some strange mpg numbers from the overhead display, the display mpg average is very accurate over a tankful of fuel, but I have noticed that the instant mpg numbers start at 12mpg (loaded truck) starting a highway trip then over 15 miles slowly increases to 15mpg, I don't know if its just my truck or what but there seems to be a change in performance and mpg as the temps increase. The only thing I can think of is the fuel timing advance changes with Intake air temp. and it takes way to long to get IAT's up especially running empty.

 

I would be woundering if the injecters are slobbering and not delivering the fuel to the cylinders in a fine mist like they should.Get some good injector cleaner put a bunch of it in your fuel an run a tank of it throu there.At kenworth a guy told me the unhook the fuel line and run straight cleaner in there to clean them.

 

Thanks for the replies, could be winter fuel and may be injectors, I'm heading out for a trip so before I see a dealer I'm going to check it out during the trip.