With my 120 something HP '89 Mazda 4wd truck, I towed all the time. Crossing mountain passes may be at slower pace, but the newer trucks have more power than what I drove. I had reasonable mileage when empty with the I4-2600, but my mileage dropped into the single digits when towing more 3500 lbs over the mountains. It was a manual transmission and the clutch and brakes lasted 100K miles towing a 8' flat bed, 16' Scamp fiberglass egg, 16' Coleman pop-up or 20' Challenger boat. After 16 reliable years, I replaced it when I bought a toy hauler and needed something that could tow over 10K lbs.