[celica]

If you are looking at the instant display you will get all sorts oif readings. You need to be resetting the display for the trip or working it out manually as the display isn't that accurate. There is a big difference with the slower speeds. Another big difference is the gas. when I tow the trailer I use premium because the truck is a pig with regular with that weight. Yes a side wind does make a huge difference, but less if you are on premium gas. your downshifting sounds normal.

How heavy is your trailer?

ps - I would never draft a semi - too dangerous for my liking and some semi drivers hate it & will do stuff to scare you (brakes, quick lane changes). You don't have time to react with how close you need to be to a semi for drafting.