3 Upgrades To Get More MPG Out Of A 6.6 Duramax

The mighty Duramax diesel engine has been around since 2001, with the 6.6-liter being the largest. Available in the heavy-duty Chevrolet Silverado and GMC Sierra, the latest iteration of this powerplant offers 470 horsepower and 975-pound feet of torque. However, one aspect of the Duramax you probably won't hear anyone bragging about, is the fuel economy. Drivers say the 6.6 Duramax has a wide mpg range and things get even worse hauling a trailer, with reports of as low as 10 mpg.

Fortunately, there are a few legal ways you can help increase fuel economy by a few miles per gallon in your 6.6-liter Duramax. First, you'll want to have your engine tuned for greater efficiency. Then, you might consider upgrading with a few aftermarket parts designed to help your truck breathe better. While there are far too many variables to say for certain what increases you'll have in fuel economy, the following three upgrades should provide a noticeable improvement.

Your truck came from the factory with stock engine settings, which can be altered to achieve better performance or efficiency. A tuner is a device that can alter several processes in the engine such as timing, transmission settings, and more. The online Duramax community of enthusiasts overwhelmingly recommend EFI Live tuning products for achieving a few more miles per gallon.

For example, EFI Live offers tools and software for the GM 6.6-liter Duramax, that can utilize optimization and economy tunes for enhanced efficiency. In fact, when asked if an aftermarket exhaust would improve Duramax miles per gallon, one enthusiast (via Duramax Forum), stated, "Yes it will help but a good EFI Live economy tune will get you a better gain."  Although, the tuning process may not come cheap, as these custom tuning files may need to be purchased separately from a vender and loaded into the tuner. Fortunately, you'd be surprised what's considered high mileage for the 6.6 Duramax diesel engine, so you should still get your money's worth.

One of the ways to improve fuel economy is by enhancing air delivery into the engine. Typically, an intake is pulling in hot air from directly around the engine. As the name suggests, a cold air intake grabs cooler oxygen away from sources of heat. Cold air is denser and therefore contains a greater amount of oxygen. This leads to improved efficiency in terms of burning fuel, and requiring less effort from the under the hood.

One example of this upgrade is the AFE Power Diesel Elite Stage 2, which was implemented in a Motor Trend build of a 2015 GMC Sierra 2500HD with 6.6-liter Duramax. According to the cold air intake manufacturer, this product boosts air flow around 44% over the stock part. This add-on can also increase performance output slightly, adding up to 9 horsepower in addition to enhanced airflow. Better yet, installation is straightforward without requiring any modification to factory parts.

The 6.6-liter Duramax features a part called a down pipe, which is a section of tubing going from the turbocharger to the exhaust system. This part helps expel exhaust gases more efficiently. One of the ways you can potentially improve miles per gallon, is to swap in a larger diameter down pipe, which can move a greater volume of exhaust gas.

One concern for diesel engines, is a creeping exhaust gas temperature (EGT). While these engines do require some heat in order to operate, if things get too hot, it can eventually lead to damage. Even just elevated EGTs place additional strain on components like the turbocharger and exhaust manifold. One of the causes of high EGT (exhaust gas temperature) is an airflow restriction. By adding a bigger down pipe, you can keep EGTs lower, enabling engine components to run more efficiently and potentially provide a slight bump in fuel economy.