gas mileage

In your opinion how much better fuel mileage does the duramax 2500hd have over the duramax 3500. The latter weights more than the former so there should be a difference but I just don't know how much. Thanks

Does anybody know the answer to this one. Mayby it was a stupid question.

If I had to guess (and i do to answer this) I would say they are probably pretty similar.