Poor gas mileage at lower altitudes?

[Eric in Wyoming]

Hi yall!

So one of the things bugging me about our Expedition is how thirsty it is at lower altitudes. I only learned about this when we moved to the Tetons in Wyoming - our house sits at 6915' above sea level. Before here, we lived in North Dakota at around 2200', and before that we lived in east Tennessee at 1000'.

In Tennessee and North Dakota we averaged anywhere from 12 to almost 14mpg. Here in the high country we're seeing just shy of 18mpg. The only things I've done to it here were two oil changes, eyeball front end alignment, and recently a dual exhaust from the Y-pipe back. We drove back to North Dakota last year for vacation, and gas mileage dropped while we were there again. Any idea why that's happening?

 

[Plati]

They say you get better MPG at altitude due to air less air pressure.
Less power better MPG.
https://www.chicagotribune.com/news/ct-xpm-2005-10-09-0510080238-story.html

Moran Junction is the center of the West for my travels.
Hope you're getting a snowmobile ... GREAT place for that.

 

[ExplorerTom]

I live in Denver and get 14. When I drive through the mountains I can get more. I think that’s because going up a hill isn’t as inefficient as going down a hill is efficient.

Let’s say you get 14 on flat ground. Going up a mountain at highway speed you might get 7-10. But coming down the mountain you’ll get 40-100. How it only averages out to like 18 is a little fuzzy to me. At least that’s what I’ve observed on my Ultragauge in my 2000 and my 2014.

 

[Eric in Wyoming]

Moran Junction is the center of the West for my travels.
Hope you're getting a snowmobile ... GREAT place for that.

Oh, I plan on it! Especially for over around Togwotee Pass area, that looks like a blast!

 

[Eric in Wyoming]

This is hard to wrap my brain around, honestly. I get making less power up higher, but then I just always figured that meant more throttle for the same cruise speed as down lower. Guess all them sensors and stuff were a good idea after all?

ExplorerTom, I've wondered that too! I think there's a point where the ECU shuts fuel off completely when you're coasting downhill for so long - my instant MPG will shoot up to 99 when it happens. Usually only does that going down Teton or Togwotee Passes, though. Roads here aren't really as up and down as I thought they'd be.