Since the GVWR of the Silverado 2500HD is so high, General Motors isn't legally required to post fuel economy figures on the window sticker. That's too bad, as it may well be a selling point.

We rented two of GM’s new crew-cab trucks: a Chevrolet Silverado 2500HD 4WD LTZ and GMC Sierra 2500HD 4WD AT4. Here’s what we’ve learned during our time and miles with these titanic trucks.