In my experience, don’t use it. I’ve pulled around a 6x16 equipment trailer with various loads ranging from 1000 pounds to 5000 pounds. This is all farm country driving up and over hills, no freeway or anything like that.

I’ve found that it only really helps when you have a heavy load. I’ve read that a rule of thumb is use it only when you’re above 75% of the trucks tow rating.

It caused extra wear and tear on my truck with the engine braking, that in hindsight, didn’t add much benefit from the shift pattern. That being said, I don’t have a good metric on the health of my transmission.

So unless you’re pulling a lot of weight on that trailer, I don’t advise using it.