There is one other thing:
When driving with a trailer, learn how not to 'break resistance.' To explain this is tricky, but resistance is defined as the point where the truck must exert a TON more force to gain only a little more speed. In most cases, the resistance point is low, meaning you can only accelerate slowly and you have to let speed build very gradually. The more loaded you are, the lower resistance is.
The way I learned is by loading a 50-lb bag on the luggage-rack of a bicycle (no I am NOT joking). Now you can pedal nice and easy like you do when the bicycle isn't loaded, and the bike will do its thing nicely and you hardly can tell the difference -other than you can only pedal nice and easy. You see, there is a point where you push just a little harder and suddenly you feel that 50lbs as a strong resistance while there is little actual change. Push even harder, and still there is little change except for your exertion. That's 'resistance.' Pedaling nice and easy while allowing the machine to do its thing is called working below resistance, pedaling harder (and noticeably so) is breaking resistance. The same holds true with a truck.
Yes, there are exceptions such as steep hills!
As for me, I like to build speed on downhills and release speed on uphills, all the while attempting to stay right below said resistance point.
Is it a challenge? You bet!
Does it save gas? Try it!
Have fun :-)