Have you ever noticed that the higher the altitude that you drive your truck that the better your mileage gas mileage becomes? On trips between Houston (40 feet above sea level) and Woodland Park Colorado (8500 feet above sea lever) I have noticed a direct correlation between the gas mileage. The higher I get in altitude the better my mileage becomes. It will be as much as one to two miles per gallon in some cases. This is contrary to what was normal for non computerized carberated engines. At first this was confusing to me. After I though about it for a little while it started making sense. The higher a jet aircraft flies the faster it will go, until it reaches the range of 30,000 to 35,000 feet. Why? Because the higher it flies, the less air it has to push, the air gets thinner with altitude. Above about 35,000 feet the air starts getting thin enough that the engines don't make as good combustion as it did getting to that altitude. With computerized engines and fuel injection the computer constantly adjust the fuel mixture and timing to maximize the performance of the engine thus getting better mileage at higher altitudes where there is less air to push. You can see my V-10 powered CC Super Duty at www.michellesfords.com go to the bottom of the page and click on other cars.

Michelle

 

Wow, Michelle. That sounds right on the money to me. I've also noticed higher gas mileage on trips at higher altitudes. Recently while at about 5,000 ft above sea level for a week camping, my grandfather's 1978 Chebby Suburban was getting 2-3 mpg better than his usual 6 mpg. I'm pretty sure it's carbureted, however, so I don't know if your explanation pertains to his "Urban Suburban" (as he has always called it ) ... but yours still sounds good to me!

Ryan

 

I don't have enough mileage to make a true comparison and haven't driven at any great elevation, but I will say this. My second tank of fuel was the best mileage my truck has gotten to date. That was coming through Pa back to Virginia on I-81 at 75+ mph and some brief low speed driving though the Blue Ridge. Truck managed to get 377 miles out of that fill and 13.6mpg. Back here in the swamp that is Florida, the mileage has fallen 3.5 mpg With the small utility trailer it falls another 2 mpg. Now I am guessing the elevation between Carlisle Pa and Lynchburg Va runs probably 400-1400'. Not a great elevation, but more than here in Florida. Seems like any elevation is better than none for mileage. I figure it is computer controls related.

 

At higher altitudes, the air is less dense, 'thinner'. When a computer checks the incoming air, it uses the weight (Mass Air Flow Sensor) of the air to calculate the fuel needed for the correct ratio. Less air, less fuel. Carbureted engines will tend to run a bit rich at high altitudes, but less air will pull less vacuum in the venturis, and use a little less fuel.