Ramcat
12-31-2004, 07:44 PM
Hi guys this is Ramcat from DTO and DTW:)
My 2003 SRW 4X2 QC 3500CTD is bone stock with just over 24,000 miles on it. When I drove it off the lot the overhead showed 19+ all the way home(60 miles). Now it shows 15+ hwy. I replaced the fuel filter, put Howes diesel treatment in the tank and cleaned and oiled the K&N air filter with no change in mpg.
I drive 65-70 on the hwy. Is this normal fuel mileage for the 305/555 motor?
Hawkster
01-01-2005, 10:57 AM
Ramcat, your mileage sounds a little low. To be sure though I would hand calculate the mileage from a full tank of fuel and see if it is better than the computer. If you are running different size tires or possibly some aftermarket electronics make the trip computer inaccurate. I have a 2500 4X4 with 4.10 rear end. Road mileage at 70 is 17.5 to 18.5 unloaded. In town 13.5-14. Towing 7k camper 12 mpg. I have the 325/600 engine so you should get better mileage than me.
kmcdonough
01-02-2005, 11:57 AM
Don't trust the overhead console. Mine has been off as much as 2 mpg. Use a calculator to get a better number. I've got an 03 3500 4x4 auto tranny and will get 15-17 on the highway. Around town I get 12-14 mpg. It seems like the guys with the stick get better mileage the the auto tranny.
precision37
01-02-2005, 02:42 PM
Where are you? It could be as simple as the combination of cold temps and winter fuel.
Cummins600
01-02-2005, 02:55 PM
The fuel mileage on these trucks seems to vary.... Great at first, then a little worse then it gradually gets better. There are some TSB's out there for the trip computers to increase their accuracy. You can have you local dealership download those in a flash for your truck. Just tell them that you are getting poor mileage and you want to know if there is a TSB out there for the truck. Try it by hand first though...see how accurate the trip computer really is.
Ramcat
01-03-2005, 05:51 PM
I did the hand calcs. The overhead is accurate. I changed the fuel filter and cleaned the K&N air filter. I saw the filter comparo in the Duramax forum and will change to AC Delco. I don't think those things will make much diff with the fuel mileage though.
Looks as though the auto tranny is the culprit.