High elevation fuel mileage

[yavapaires]

Does anybody have an explanation as to why my 96 4.0 OHV V6 gets better fuel mileage in Az at higher elevation (5000ft) than it did at 1150 ft elevation in Nebraska? In Ne I was getting 17.5 to 19 mpg, in Az I am getting right at 20 mpg. The only thing I can think of is the Ethanol content, 10% here vs 15% in Ne.

 

[RomeovilleIL]

Fuel very possible - ethanol does get lower mpg. Wouldn't be shocked if the aerodymanics of truck plays into it too. You are in thinner drier air, with a lot less wind in Arizona than back in Nebraska.

 

[koda2000]

At higher altitude there's less available oxygen. Your ECM adapts for this my adding less fuel keeping the air/fuel ratio optimal. with less air and fuel going into the engine it produces less power so it has to work harder to achieve the same performance. that's why your MPG isn't as good at higher altitude.

scratch that. I just re-read your post and you're saying you're experiencing the opposite (better MPG at higher altitude)... i got nothing

 

[Turdle]

Koda had the correct answer. Less air at higher elevations. This will give better economy. I've noticed this every time we drive to Colorado, in every ecm controlled FI vehicle we have owned.

 

[yavapaires]

I have lived in Az for over 45 years, and have never experienced this before. I have taken many trips to Phoenix where I have gotten better mileage and performance with both carbureted and FI engines.I was just wondering if Ford has more than one program for this engine. By the way,Nebraska sucks bigtime. I am glad I went there, but damn glad to be back in Az. Thanks for your all's thoughts.

 

[MNgopher]

Nebraska fuel has the same ethanol content as anywhere else - 10%, if there was ethanol in it.

Lower air density is part of the reason for the better fuel mileage in AZ - I usually note the same in Colorado and Wyoming versus Minnesota.

 

[yavapaires]

Funny,but for the 19 months I lived there, the ethanol content was 15% around Omaha

 

[MNgopher]

Your basis for 15% is based on exactly which information?

I'll make it real simple. You are wrong about the 15% ethanol content in Nebraska. If you were using E15 from a special "blender" pump, you did so in violation of federal law.

E15 was not approved for use in 2007 and later cars until late 2010 by the EPA. It was approved for use in 2001 to 2007 cars in January of 2011 by the EPA. As of the end of October of 2011, it had not been rolled out for mass consumption use in Nebraska (other than at specialty blender type pumps allowing blends from E10 to E85) according to the Nebraska Corn Board, whom I am guessing would promote its use rather heavily if it were available. All signs point to the first availability sometime in 2012, according to the University of Nebraska as well.

If you were buying fuel with ethanol in it at a general pump, it was E10.

 

[yavapaires]

Your basis for 15% is based on exactly which information?

I'll make it real simple. You are wrong about the 15% ethanol content in Nebraska. If you were using E15 from a special "blender" pump, you did so in violation of federal law.

E15 was not approved for use in 2007 and later cars until late 2010 by the EPA. It was approved for use in 2001 to 2007 cars in January of 2011 by the EPA. As of the end of October of 2011, it had not been rolled out for mass consumption use in Nebraska (other than at specialty blender type pumps allowing blends from E10 to E85) according to the Nebraska Corn Board, whom I am guessing would promote its use rather heavily if it were available. All signs point to the first availability sometime in 2012, according to the University of Nebraska as well.

If you were buying fuel with ethanol in it at a general pump, it was E10.

Sorry,I guess I'm mistaken. I could have sworn the tag on the pump said 15% ethanol. I may be loosing my mind I guess. Sorry to have ruffled your feathers. I guess you're the expert.

 

[Texas97x]

Yavapaires, I'm with you. All the pumps around here say E15. I have never seen or heard of E10 in my 47 years on the planet. I'm just sayin'......

 

[SoNic67]

10% is the "normal" maximum blend. Otherwise the pump should have this label:

So you might have beeing using the E15. That will get less gas milage, is illegal and... will damage the engine in long run.

Now, about altitude.
Less air pressure means less MAF signal, therefore less gas in injectors. Sure, that would result in less power. That usually makes people stomp harder on gas pedal till the normal levels of power are attained - bringing back the gas (and air) flows. ECM and O2 sensors will take care of the right mixes (even if that means adjusting the long term fuel trims). So it is not that reason for different mpg.

BUT... lower air pressure means also less drag. On our square Explorers, that makes a BIG difference in mph, especially at 80mph (in AZ that's the norm). In order to get to 80mph with less air pressing against front of vehicle, you need less power (less gas).

PS: If I drove behind a tractor-trailer, I got extra 3-4 mpg at 65mph (measured with reader plugged in the OBDII port). At 75 mph my milage goes down 1-2 mpg compared with the one at 65mph