F-150 through F-350 are all considered light vehicles. The 450-650 are Medium Duty. The 750 other trucks are considered Heavy Duty. (For GM vehicles append anot

F-150 through F-350 are all considered light vehicles. The 450-650 are Medium Duty. The 750 other trucks are considered Heavy Duty. (For GM vehicles append another 0 eg, 1500, 2500, 3500) Calling 250s and 350s Heavy Duty is mostly marketing, although, the current 3/4 and 1 Ton trucks are more capable than ever, so the marketing inflation does have some basis. https://en.wikipedia.org/wiki/Truck_classification https://en.wikipedia.org/wiki/Truck_classification