Getting this kind of real-world data is rare, but we drive the all-new 2020 Chevy Silverado HD 2500 nearly 1,000 miles to measure its highway MPG and DEF (Diesel Exhaust Fluid) usage. Does the new 10-speed automatic transmission improve empty highway fuel economy?
2020 Chevy Silverado HD
This is indeed an all-new heavy duty truck. It has an updated frame. The crew cab wheelbase is longer than before (by about 5.2 inches). The whole truck is bigger, including about three inches of additional rear seat legroom than before.
It has a completely unique body design, but it does share the roof and many of the interior/dash components with the new 2019 Chevy Silverado 1500 trucks.
The turbo-diesel engine remains mostly unchanged. It is still the L5P Duramax 6.6-liter V8 with the same output rating of 445 hp and 910 lb-ft of torque. The engine has improved air flow and cooling capability to handle heavier loads. The 2500 HD diesel truck is now rated to tow up to 18,500 lbs. The maximum 3500 HD dually towing number is 35,500 lbs.
The big change is the 10-speed Allison-branded automatic transmission. It replaces the 6-speed Allison automatic that was there before.
Spoiler Alert: after the long Oregon – to – Colorado trip, the final highway MPG result was 19.9 MPG according to the fuel pump calculation. I also saw about 1,012 miles on one gallon of DEF, according to the pump.
The new Silverado HD crew cab has a 36 gallon fuel tank and a 7 gallon DEF tank. This gives the truck over 700 miles of highway range when running empty. It also mean that you could potentially go about 7,000 miles on a full tank of DEF. However, the DEF system will give you several warning messages when the system estimates about 500 miles remaining on DEF. You do not want to run the truck close to empty on diesel exhaust fluid. The truck will eventually go into limp mode when the level gets very low.