So I work on Subase Bangor. I have always said, what a government vehicle has in miles at least double that...tons of different drives, idle time, short trips yada yada. You get the pictures.
The use a lot of GM, Ford and Dodge trucks. The cars are well you name it. Mopar, Ford, Toyota, Chevy, Hyundai. It is a hodge podge.
The have recently updated all the S-10s and Canyons/Colorados
They use a bunch of the 2.8 Duramaxs and the code I am in has one of those and a 3/4 ton Chevy van with a 4.8.
The little Duramax has just over 30,000 miles on it. Everyone likes it. I drive it a few times week and have to say I really like. Has plenty of power, is quiet and smooth
I couldn't tell you about gas mileage, but it has only has 1 oil change.