I don't know, but that seems like a low price. I have a 2014 F-250 4x4 Crew Cab with 50K+ miles on it and KBB (for "Trade in") in "Good" condition is still mid $30's. Now granted it's the Lariat model, but I would have thought even a moderately equipped 2015 2500 Silverado (4x4 crew cab) would be close to that, unless it's really high miles or in rough shape. Also mine is GAS as well. I too would like a Diesel, but my wallet must have talked with yours, because I think it has the same opinion.