MPG in the Rain?

Forum: Does anyone know how much driving in the rain effects MPG? I measured my MPG a few days ago, I got 19mpg in some really bad weather. Any idea of what I can expect in good weather? I'm guessing at least 10% better?
Anyone have some testing on this?

TIA

R

 

Not really, I was driving 65-75 most of the time.

 

I never noticed a difference in mpg. I imagine there is slightly more drag going through rain, but the rain also cools the air so you make slightly more power? Sounds like something for mythbusters to solve.

 

There is no way to give you an exact answer. It depends on how hard it is raining and if there is wind or how much wind. Rain will lower your MPG because of drag, both at the tires and the body, but it will vary depending on the things I mentioned.

 

In theory the denser cooler air would improve your power and mileage. In practice you can't detect the difference with your ass in a seat or measure it with calculator at the pump. So, for all practical purposes, no improvement.

 

I cannot prove it but my truck seems to have higher rolling resistance during a heavy rain at highway speeds. As stated above maybe myth busters could do a test. As it is there are so many variables with temperature, humidity, barometric pressure, wind, hills, stop and go, etc. that it is hard to quantify.

I am certain that when I hit a deep puddle at highway speeds I can feel the increased drag as I hope to avoid hydro planing.

 

Like the post above I completely agree with the increase in drag during a rain storm. Maybe it's just my bfg ko2's but when I head through an area with any acculumlation of precipitation I can feel the truck slow down ever so slightly. Amplify this over the course of a number of miles and you will, in my scientific opinion, have reduced fuel mileage. How much? I have no idea!

 

REALLY...WGAF

 

^^This^^

Make sure you take into account regional pollution levels....aka Acid Rain...as I'm sure the particulate matter conentration per rain drop has a direct impact of the H2O drag coeffecient and tencil strength of each individual rain drop. Also, the brand and efficiency of the wax may play a role in overall aerodynamic characteristic s, which would impact mpg. Any scientist out there who could come up with the proper formula?

Forgot about Rain-X.....crap..that changes everything.

 

In anything other than extreme weather, significant snowfall, or while towing, my truck has returned between 18-19 MPG mixed driving. On highway only it's 20-21 MPG. I've seen these same basic numbers since the day I bought it.

Unless you were driving in a hurricane, I don't think you'll see any difference that can be attributed to the rain. I find the mileage on my truck is extremely predictable.

 

IMO the only wheater that sould affect MPG is cold because heating up the truck before leaving and snow because of

 

If cool dry air is the best for making power, and I believe it is.
Then extra water vapor that will not burn, can't help.
I was hoping for some real world data?
Going by the responses, it does not seem to be an issue.

 

Wind usually comes with rain so depending on direction it could either add or subtract to MPG

 

Water vapor can improve combustion by cooling the air-fuel charge and controlling detonation. You can even buy a kit to inject water or water and methanol. Back in the day hotrodders would use a pump, a windshield washer reservoir, tubing, and a nozzle to squirt water directly into the carburetor.

 

It all depends on if you drive with the tide or against it..

 

7.3

 

Wheelspin everywhere for me... Supercharger problems

 

Rain means low pressure, warm moist air.

High pressure is cold, dense, dry air. That makes the most power. I've noticed it time and time again, those crisp cold clear November nights, where the stars are out and it's a few degrees above freezing, my car wants to go, like its chomping at the bit.

 

It was my understanding that the water vapor in the air displaced the oxygen.
Just like when we increase altitude and decrease power, less oxy.
I can see the experience of the forum does not agree.

R