Humidity and gas mileage

[Mondo Limbo]

I live in Texas where it's usually pretty dry.  When the humidity is very high my gas mileage gets much better.  Could that be a sign of running too lean, or something along those lines?

[Grumpy]

Nope, moisture in the air helps the fuel charge expand when it is fired. Was a trick that was used in WW2 to increase horsepower in some of the bombers and a couple fighters. They were equipped with water injection to boost power. I have noticed the same thing with my dodge hemi acts like it picks up a few on a foggy or humid day.

[PhredValk]

That would explain why I get better mileage in Southern Ontario (Great Lakes makes it generally very humid) than I do on the prairies (where it's generally dry).
Fred.

[pancho]

Ditto what Grumpy said about some WWII fighters and bombers, over the years I have heard tale of it being used in other motors as well. Hmmm,, makes you wonder if you could rig up an apparatus to atomize water and introduce it into the airbox below the filter in the right proportions.........  lets see, two custom cans on two of the header pipes to vaporize the waser,, a five gallon can for the water strapped on the sissy bar............

[Pappy!]

The charge is cooled by moisture. Cooler air is more dense. Also supresses detonation to a degree. My Uncle flew P-61 Black Widows during WWII. His engines were 2,000hp on gasoline and almost 2,500hp on water injection. Said he could almost stand the airplane on it's propellers.
There are several companies out there making alcohol injection at this time for cars.

[Oklahoma_Valk]

Wow! Incredible information.

[t-man403]

Yup, nothing new by any means.
I don't know about today, but back in the day, water injection was used on the drag strip.
It's also an effective way to blow out carbon deposits.