For the LB7 Duramax, the Flashpaq offers four power levels above stock: Mileage XS, Tow, Tow/Perf and Performance. Moving on to the LMM, leaking transmission cooler lines will have to be addressed sooner rather than later. 5.3L Vortec MPG Mods. Longer-Lasting Engine. Gas mileage is notoriously poor on all trucks, not just Chevy’s and not just the 5.3 vortec. As a consequence, there is a direct impact on the environment. http://www.powerupdiesel.biz Looking for better fuel mileage with your Duramax diesel? Even on the LBZ, one of the most durable versions of the Duramax ever produced, there is still room for improvement in the form of addressing the transfer case pump-rub issue in 4x4-equipped HDs. Exhaust gas temperatures usually drop on average 150-250 degrees depending on the system. 2015.5 GMC Sierra 3500HD Denali SRW 6.5 bed - iridium metallic - Aug 17, 2015 Deleted @ 10,000 miles w/ Fass 150, Flo-Pro 4" stainless, Pypes 4" to 6" tip, FTE Resonator, PPEI tunes, … I have friends that changed diesel source and found mileage improvement (wasn't duramax, but was a diesel). If the … Better mileage … 2015 Chevrolet Silverado … As far as mileage, it's hard to tell pulling a 5th wheel because there are so many variables. Around town, the average seems to be in 14 mpg range (without a trailer of course). Just 2 bolts behind the catalytic converters.Chevrolet 4.8L/5.3L Over all, we averaged 10.1 mpg. The truck still has just over 2K on it, so I'm hoping as time goes on and I switch to synthetics the mileage will improve … The back pressure myth has worked for me for the last 2 weeks with gains of about 4 - 5 mpg. While up to 119 hp and 206 lb.-ft. of torque can be added to that Duramax engine … Duramileage custom tuning can give you up to a 4-7 MPG gain. Every smart alec’s response to “how do I improve my trucks gas mileage?” is “buy a … If testing fuel source, I'd try any new sources for several tanks before … The most accurate 2015 Chevrolet Silverado 3500 HDs MPG estimates based on real world results of 1.3 million miles driven in 51 Chevrolet Silverado 3500 HDs ... 2015 Duramax. Use our handy tool to get estimated annual fuel costs based on your driving habits. Most of our customers report 2-3 mpg fuel economy increases and much freer, quicker revving engine. If fuel economy is improved and there is an increase in the fuel mileage of engines such as the 6.7, we can help contribute to the betterment and protection of the environment. View detailed gas mileage data for the 2015 GMC Sierra 2500HD.