I drive a small automatic car. For the most part, it struggles a bit with steep uphills, and picks up speed when going downhill. That’s to be expected.
But then I noticed some downhills actually slow it down. I’ve noticed during a two-hour motorway trip I often do to visit family, there are some specific downhills, not all, just some, where my car always slows down and I have no idea why.
Ideas?
engine braking ?
This is very likely the reason. Not all downhills will induce it, but the automatic is down-shifting to slow your acceleration. There are various ways for your car to know but manufacturers want the driver in control, not the environment. Depending on the car and speed you may not hear it, but when it slows down does it sound like the engine is revving higher?
It also helps keep brakes cool, important for mountain driving.
One of my cars hardly does any automatic engine braking. My other vehicle will keep or decrease speed down long hills/mountains. No noticeable change in engine noise at all. Makes long trips through the mountains much easier, especially because it’s a heavy vehicle and overheated brakes is a very real concern.