transamsam98

iTrader: (56)

My brother has a 06 2500 cummins with a custom intake with K&N filter, Quadzilla Xzillaraider Performance Chip XZ2003R, 38" bf goodwrinch baja's on stock wheels, 5 inch turbo back exhaust, the silencer clip out of the turbo, and a smoke out kit on it.

The vehicle is getting about 10-12 mpg on average and the instant fuel economy reads about 14-16 consistently. The fuel economy does noticeably increase right after the air filter is cleaned and drops back down after about a 1/4 tank through.

Any ideas Why my brother is getting such horrible fuel economy other than the tires?before the tires it averaged 20-22mpg with all listed mods except the tires. after the tires it dropped to 16-18mpgs on average and has recently dropped to 10-12mpgs what could cause a 4-6mpg drop?

TransAmatt99

iTrader: (24)

you have a 9000 lb truck turning 38" tires...you should be happy your getting 12, a gas engine would be in the single digits.

cdub81

iTrader: (2)

was his calculation by the instant mpg in truck or did he do the mpg to miles math yes the tires def hurt and with the chip whether its plug and play or obd 2 it will trick the instant mpg readout in the truck.... He could possibly have a bad injector or 2 bad injectors that will drop mpg. i had an 06 mega cab cummins 6spd with all that bs on it on stock tires and never really got better than 16-18 mpg even though the instant mpg was sayin 27mpg

BigRed Cummins

A lifted diesel with tons of fueling mods and 38 inch tires with stock gearing isn't going to get much better. Re-gearing it will not only make it faster and more efficient, it will help the tranny live longer.

overdrive

With bigger tires, you have to have the computer reflashed for the correct tire size. Probably not seeing the correct mileage on the odometer to calculate the mileage.

Randy

Blown06

iTrader: (32)

Just an FYI, my 06 cummins shows about 24-26 mpg on the factory gauge on a consistant basis. When checked with a calculator it gets 18.5 everytime, regardless of how I drive it.