Here is something very strange. I bought my FEH from sea level and brought it to Denver which as we know is the mile high city, I was averaging about 33 MPG with it and then after I had disconnected the 12 volt battery which would reset the computer, now I am averaging about 38 MPG. I have given it a few months and it is stable at 38, why am I now getting 5 MPG better than previous with just resetting the computer? I have one or 2 theories and just wanted to see if anyone could confirm or dispell. Denver has roughly 17% less oxygen in the air and going from 33 to 38 is roughly a 17% increase, is this coincidence or is the computer calculations thrown off by the reduction in oxygen levels, or with the less oxygen in the air am I just somehow getting 17% better MPG?

 

Changes in gasoline type? You didn't mention where you were at sea level and if they are using Ethanol in the gas in Denver.

Also, is this the first computer reset you've done since owning the FEH? Did someone own/drive it before you?

 

I've noticed as well that I get phenomenal gas mileage at altitude as well. I attribute it to the long downhill runs I make and the fact that the ICE has almost no load on it, basically at idle. Short bursts of heavy load going uphill and then long downhill runs. I went from Hinton, AB to Calgary, AB (almost 500km) on a little over a half of a tank because of the lack of engine load.

Just my 2 cents.

 

I live at 5000 feet in Payson arizona, and see great gas milage mainly because the air is thinner and resistance at highway speeds is hugley less. You will also notice that the higher the humidity is, the less your milage on the highway. Air gets much thicker at even 20% humidity, and when there is a fog - the antenna even whistles! I saw 1% humidity this week here in arizona, and my mileage on my 90 mile drive to work hit over 43mpg average. ON a humid day, that can be as low as 36mpg. Food for thought!

 

I see where air density could play a part in this.

With highs in the high 90's and 80% humidity in the local forecast, I guess I'll be lucky to stay in my normal 34-36MPG range.

 

Almost everyone thinks the opposite, but humid air is less dense than dry air. As a pilot, that is part of the all-important density altitude. Hot and humid means the least dense air.

 

It is not just hybrids. My 2003 Honda CR-V got it's highest ever MPG at high altitudes during a vacation to NM and Colorado a few years ago. I managed 35 MPG at 70 MPH (average).