Is it the oxygen content, aerodynamics, or something else?

January 20, 2020

2019 Ford Raptor

Do trucks and cars get better fuel economy in the mountains rather than in the plains? This question comes to us from Jeff B. who recently purchased a 2nd-generation Ford Raptor.

Jeff writes:

I’ve never seen anyone tackle this topic. I think it might be a great segment for you if you haven’t already done it. It took many years of heading up to Summit County (Colorado Rocky Mountains) to realize that I get better gas mileage in the mountains than I do on the plains. Here’s the quiz of the day for the mighty TFL team: Why do you get better MPG in the mountains than on the plains?

Jeff did not provides any MPG numbers for comparison, but we have been testing trucks in various conditions for over six years. There is one simple reason why trucks and cars can get better MPG at higher elevation (in the mountains). The air density is less at higher elevations. The air is leaner and not as packed with oxygen as it would be at sea level or lower elevations. Thus, the engine is running leaner as well as it’s trying to manage the air/fuel ratio. This can result in better efficiency at elevation.

Yes, you need to use extra fuel climbing a grade. Turbocharged engines can make up for lower air density, but gentle use of the throttle and long downhill sections can and often do result in increased fuel economy.

What do you think? Is it also affected by aerodynamic drag? Let us know in the comments below.