GM releases details on upcoming 4.5L Duramax turbo-diesel V8 - Autoblog
looks like a great motor for people who want more towing than a traditional 1/2 ton but dont need as much as a 3/4 ton or 1 ton pickup. also it will give you more power and better fuel economy than the normal small block equipped 1/2 tons.
however, while i do see myself buying a new truck within the next 5 years, i dont see this being one of them and here's why: the motor will probably be a 1500+$ option like the current hd durmamax 6.6. And on top of that diesel is about 60 cents more per gallon than gasoline. so while im sure the motor will get much better mileage than a normal small block, i doubt it will be so much better as to make up for the extra cost of buying diesel over gasoline.
plus since i live in corn country i have easy access to e-85. which is about 40 cents cheaper than e10 (89 octane), about 60 cents cheaper than 87 octane and about 1.50$ cheaper than diesel. plus, i do some towing from time to time but the small block has always been just fine for me. and i guess if i was real serious about towing i would just get a hd pickup.
so while its a sweet motor and im sure this motor will help with government mandates and might make the hippies feel a little better, it seems like kind of a pointless motor.