[encantotom]

i can only speak to a 2013 isx15 rated at 500hp on a cascadia super c weighing all in at 38k lbs. it has 45k miles on it, with a eaton 13 speed ultrashift. pulls like a freight train. doesnt slow down going up hills. got 8mpg on a 9k mile trip this summer. the 650hp i am sure has different injectors,, maybe cam and not sure what else.

i have several buddies who manage fleet truck repair centers and they love the isx. i had zero issues on my last trip.

compared to the series 60 in my 53k lb newell, the isx pulls stronger, but the newell weighs alot more.

my two cents worth

tom