Why can't trucks have smaller engines?

Wouldnt it be good to have a truck with like a ford escape 4 cylinder 26mpg engine? Does it have to be made for power?

They already do. Most all new light duty full sized Ford pick ups are v6 and v6 turbocharged. But there gas mileage is still close to everyone else's v8. Technology is getting better everyday. And the v8s are gaining… V6 and v6 turbo put out more hp than v8s did 5 years ago… Most people are stuck in the olden days equating hp to engine size

The primary purpose of a truck is to haul cargo, This means power is required. Power means a 26 mpg Escape 4-banger isn't going to cut it.

The main purpose of a truck is to work. They are designed to haul cargo IN the truck and to tow trailers behind. A small 4 cylinder engine in a full-sized pickup truck wouldn't be able to haul weight OR accelerate to keep up with traffic on a highway as needed.

If you want 26 miles per gallon, then BUY the Ford Escape instead of a pickup truck.

A truck with an escape motor would still burn a lot more fuel. Weight and aero matter more than engine size.