Once the diesel rolls out for the 2020 Silverado, it will take the title of most fuel efficient full-size truck on the market with an EPA rating of 23 City / 33 Highway / 27 Combined. The 3.0 liter inline six-cylinder diesel generates 277 hp and 460 lb-ft of torque. The diesel is mated to a 10-speed automatic transmission and also features a start stop system. In the Silverado, the price of the diesel engine is the same as upgrading to the 6.2 liter gasoline V8. It adds, $2,495 to the price of an LTZ or High Country model, or $3,890 to the cost of an LT or RST. Naturally, the engine will be available in the GMC Sierra as well. For those counting, this means the Sierra diesel is more efficient than the 4-cylinder diesel in the Chevy Colorado and GMC Canyon. It is also a less costly upgrade than on the two smaller trucks, there costing $5,745 on an LT
GM is likely to hold the MPG title for a while as Ford's F-150 diesel was just released for 2019 and is rated for 22 City / 30 Highway / 25 Combined. Ram hasn't sold their 3.0 V6 Ecodiesel since 2017, but it was rated at 20 City / 27 highway / 23 combined.
Honda does not field a full size truck. Nissan does, but does not offer a diesel in their standard duty models. Toyota does not offer a diesel at all, though it is rumored that the next Tundra will be coming with a twin-turbo V6 hybrid.
The Silverado Diesel arrives in dealerships this fall.