Some years back when we were new to fifth-wheeling, we lugged our big new fiver “up the hill” in New Mexico. According to the guidebooks there was a wonderful campground, beautiful views–well, you get the picture, and it was WAY up there above 10,000 feet. Well, as I said, we were new to fifth-wheeling, and our rig was as heavy as anything we’d ever towed.
The views were remarkable, and the air clean, crisp, and vibrant. But somewhere short of the wonderful campground up at the top, it all started to unravel. The farther we went, the harder the climb, and no matter what we did with gears and gas pedals, it just seemed we were going slower and slower. Finally, in sight of the campground, pedal to the floor, gears down as low as we could go, our forward momentum dropped to less than five miles per hour. The road was narrow and turnouts, none.
If you could’ve operated that truck engine on sweat, we could have gone on forever. We had visions of rolling backwards down the hill to the nearest curve, and quickly making the rest of the way down airborne. We somehow managed to crawl our way to the campground entry–and it was closed.
We’d unknowingly stumbled across a phenomenon that some newbies are hit by: Engine horsepower can be affected by altitude. “Can be” means, if you have a ‘normally aspirated engine’ you “will be.” Vehicles equipped with a turbocharger or supercharger (for all practical purposes) aren’t affected by high altitudes. But for the rest of the world, your typical gasoline engine vehicle will be horsepower impaired the higher you travel.
What kind of “hit” can you expect? The rule of thumb is this: For every 1,000 feet of climb above sea level you’ll lose 3% of your horsepower. Moral of the story? If you’re “pushing it” to pull your trailer or move your motorhome around at a couple thousand feet, beware the mountain ranges.
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