Some things are worth the wait. A few weeks after GM reported that the 2020 Chevy Silverado’s Duramax engine was delayed due to emissions certification, the results are finally out.

After testing the 3.0L inline-six at the Indianapolis Motor Speedway, GM’s engineers walked away impressed with the engine’s fuel efficiency. According to internal reports, the LM2 Duramax was able to achieve 30-40mpg when traveling at 50-65mph.

While it should be noted the mpg rating came from a controlled environment test, it shows the potential of the new Duramax to break the 30mpg barrier — a feat previously unheard of among diesel pickups. A fact that Silverado’s chief engineer Tim Herrick called “extremely impressive”.

This was not a one-time fluke either. At a media event last week, auto journalists were given a chance to flog the engine in a 15-mile closed track. A number of drivers were able to surpass the 40mpg achieved by GM, while others reported getting 30mpg.

At present, the Silverado’s closest competitor, Ford’s venerable F-150 gets 22mpg in the city and 30mpg on the highway via its 3.0 Powerstroke diesel, for a combined EPA rating of 25mpg.

Part of the Silverado’s better fuel economy is due to improvements in the engine itself. The inline-six is an all-new cleansheet aluminum block that’s 25% lighter than a comparable cast-iron mill. Besides the aluminum block and pistons, the engine’s only iron parts are the crankshaft, connecting rods and cylinder liners. It also uses a new variable intake for optimum engine operation under different loads, as well as a new low-pressure exhaust recirculation system.

But GM may not hold the efficiency crown for long. Fiat Chrysler has announced that the Ecodiesel version of the 2020 Ram 1500 will have “class-leading” fuel economy, a statement the General has yet to challenge.

But no matter who wins the mpg war, it’s already a victory for us diesel lovers. Stay tuned!


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