I use an app to keep track of my mileage. Too bad the app could not flip to non metric. It gives me km per liters. As you could see in the pic chart, the low reading are when I tow my A128S, lowest on hilly roads, the mid are city driving without TT, and the high are mostly highway trips without the TT.
Best=9.5 l/100km Worst=21.2 l/100 Avg=15.5 l/100km
2007 PONTIAC Torrent SUV gets 12-15 MPG towing A128S
Nice to know the MPG of other campers