Why highway is better for cars?

My car Honda civic 1997 550km with 1 tank Montreal-Toronto

Is very economical on highway

Added (1). The engine loves highway?

Added (2). Keeping the car healthy

Do a lot of highway?

On the high way, you typically drive at a constant speed. The engine has to keep a constant speed and is not constantly accelerating. A lot of stop-and-go driving lowers your gas mileage as the engine has to work hard to bring the car up to speed, and then slow down, and then speed up, and so on.

Imagine carrying something heavy at a constant speed. If you were stopping often, you'd tire out faster since you need more energy to move the heavy object.

There are some other reasons, but this is one of the main ones.

You are moving at a steady speed. You are likely using your brakes less. If you look at a fuel economy curve, there's a certain rpm range where fuel economy is the highest.

Hi so actually it is asking a lot of a 20 years old car to do that sort of distance chances of breakdown are most likely.