I have searched through some old posts and can't find an answer even though I'm sure it's been asked before. I have 2 03', quad cab, 3500, 4x4's w/the Cummins. One is a single rear wheel with 3:73 and one a dually with 4:10. I can get up to 19mpg and average 15-16 with the single rear. The best I have gotten with the dually is 12.8 mpg hand calculated. Both rigs have 30,000+ miles, no towing, normal driving, 48re tranny's, normal maintenence, no load etc. I do have a contractors rack on the dually but I average 11-12 mpg which seems low especially when so many run in the high teens. Any info would be great. Thanks, E.

 

under the regular maintence do you change the fuel filters every 15k or sooner? the 4.10s will be running at higher rpms so the mpg's should be a little less then the 3.73 but there is a big difference. who is driving the dually? maybe if its one of your employees, he has a haevy right foot

brett

 

put about 8 ton behind each and take them for a day long drive up hills and your milage will go up you need to work them it will take 100,000 miles to break it in if you never tow heavy

 

If you have never used injector cleaner I would try some. I highly recommend Lucas. I gained 2 mpg after using it. I now use it every 2-3 tanks of fuel. Not a miracle cure. If the injectors are dirty it will help, if they're not it wont.

 

Have the same duallie . I had the same problem.....Took it to the dealer and told them to reflash it. It was running rich so sucking the fuel worse. Got about 5 more miles to the gallon...................

 

I'll try the re-flash. I do change the filter every 15K and I the only driver and I drive like an old lady. I will try some injector cleaner also. Both trucks have led a very easy life so far so the break in could still be an issue but the re-flash will get done hopefully next week. Thanks for the info guys!!!