Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - Does fuel economy get better with altitude?

CobraBall · 07-04-2009, 04:51 PM

Regarding aircraft mileage and altitude.

All aircraft engines (reciprocating, turbo-prop & jet) maintain approximately the same air to fuel ratio at all altitudes. As an aircraft climbs there is less O2 air molecules per gulp therefore less fuel is consumed (ratio remains the same). At +/- 18,000 ft. the amount of O2 available is 50% compared to sea level (on a standard day) thus fuel burn decrease approximately 50%.

Less O2 also means less power unless you are turbocharge. Less O2 also means less air meaning less resistance BUT it also means less horsepower, shaft horsepower or (jet thrust) available.

All other thangs being equal, humid air will result in less horsepower because the moisture molecules will displace O2 molecules. This gets into DENSITY ALTITUDE problems, see Density altitude - Wikipedia, the free encyclopedia

If you want really good gas mileage move to Leadville, CO. or Tibet.

07-04-2009, 04:51 PM	#3 (permalink)
CobraBall EcoModding Apprentice Join Date: May 2008 Location: North Texas Posts: 112 Thanks: 0 Thanked 2 Times in 2 Posts	Regarding aircraft mileage and altitude. All aircraft engines (reciprocating, turbo-prop & jet) maintain approximately the same air to fuel ratio at all altitudes. As an aircraft climbs there is less O2 air molecules per gulp therefore less fuel is consumed (ratio remains the same). At +/- 18,000 ft. the amount of O2 available is 50% compared to sea level (on a standard day) thus fuel burn decrease approximately 50%. Less O2 also means less power unless you are turbocharge. Less O2 also means less air meaning less resistance BUT it also means less horsepower, shaft horsepower or (jet thrust) available. All other thangs being equal, humid air will result in less horsepower because the moisture molecules will displace O2 molecules. This gets into DENSITY ALTITUDE problems, see Density altitude - Wikipedia, the free encyclopedia If you want really good gas mileage move to Leadville, CO. or Tibet.