Drop in altitude Drop in MPG??

[TexasCrane]

7K isk ? Is that the elevation of Flagstaff ?

Yes

 

[OverLand Cruisers]

Yup. However it is pretty easy to get over 9K on nearby FS roads/trails.

 

[DuckLN]

One other variable in a sea of variables is that refineries produce many different chemical structures or blends of product. Im told the cleanest burning fuel is sent to LA while the least refined (or dirtiest burning) is sent to places like arkansas and mississippi. Im not a chemist and could not comment on btu variance from one blend to another but hey its just more knowledge in your game.

It sounds like youve proved your point that elevation does have a measurable impact on fuel economy.

 

[Peru Darrell]

Your mileage is strange. I regularly drive from 6000 to 15,000 ft & down to sea level and always get better mileage when down on the coast. Next time I will log it both ways. About 22km per gallon on the coast and 14-19km/ gal at altitude. It is not fast driving like in the USA only about 80km/hr maximum, normally maybe 60km/hr. Along the coast I even drive faster because the roads are straighter. I have the 1FZ FE 4.5l motor.

 

[2001LC]

Your mileage is strange. I regularly drive from 6000 to 15,000 ft & down to sea level and always get better mileage when down on the coast. Next time I will log it both ways. About 22km per gallon on the coast and 14-19km/ gal at altitude. It is not fast driving like in the USA only about 80km/hr maximum, normally maybe 60km/hr. Along the coast I even drive faster because the roads are straighter. I have the 1FZ FE 4.5l motor.

So at altitude is 6,000? ft.? What do you suppose is reason for 14-19km/gal variance? Octane? Be interesting to see what you get off log info.

 

[CA Cruisin]

The higher in elevation you go, the less oxygen (lower atmospheric pressure) so the computer injects less fuel to keep the mixture right. Back in the day, cars sold in Colorado had smaller jets in the carburetors to compensate for the altitude. Occasionally, people visiting from sea level would have their cars stall out on some of the higher mountain roads because the fuel mixture became too rich.

The trade off is you also lose power the higher you go, I believe it is 3% drop per 1000 feet in elevation gain. That means if you live in Denver, your car has 15% less power than at sea level. At the Eisenhower Tunnel on I-70, you are down to 2/3 the power you would have at sea level.

Thanks for this explanation. Explains why we managed 17-18mpg in the loaded Cruiser @ Lake Tahoe this past February. Elated! At sea level it gets 13-14 mpg max. Definitely less horsepower driving up to Kirkwood but hey what's the rush, with views like these!

 

[Peru Darrell]

So at altitude is 6,000? ft.? What do you suppose is reason for 14-19km/gal variance? Octane? Be interesting to see what you get off log info.

Altitude is anywhere from 6-13,000ft normally with trips up to 15,000. The big variance for me is to that a lot of the "roads" are more like trails and have to be driven in lower gear (2nd or 3rd on my 5 spd manual) There is very little highway, high speed, driving here.

For Gasoline I use 85 or 90 octane depending on what is available.