Lost gas mileage in the rain

[circa1986]

Has anyone else noticed much worse gas mileage when driving in rain? I can't quite put my finger on it. I doubt it has to do with aerodynamics or rolling resistance being affected by the water, but I have trouble believing that the electricity used by the wiper blades, defroster and headlights (and thereby taken out of the IMA battery) could cause such a big difference. I'm talking like 3-5 mpg here!

Could it be the wind? What gives!?

[circa1986]

Sweet, I will have a 22mph tailwind going home today, maybe that will make up for this morning's 40 mpg commute!

[lat.ch.]

I dropped to closer to 35 mpg during a couple hour jaunt on the interstate in the rain. Of course, in my first 4800 miles, I've had only two or three tanks of 40 or 41 mpg so far and my best one was 43.

My car doesn't seem to like SW PA and WV hills. Or rain. Or snow. Or the occasional ladder on the roof. Or 70 mph or so. ...

[firsthonda]

Originally Posted by circa1986

Has anyone else noticed much worse gas mileage when driving in rain?

I do. I think it has to do with the wet pavement and use of the defroster.

[freddy the mug]

DEFROSTER-- you are using the a/c.
In 13k miles my a/c has been on 4 min total.
But I'm only now getting up to 53mpg.

[Cobb]

All of the above. The water from the sky makes the car use more effort to move forward as well as the wet road makes more resistance to rolling and aero. Lets not forget the power necessary for defroster, wipers, fog and lights too.

[Escot]

You cant overcome drag and friction without a price. On my Third Honda Hybrid. 1st Gen, civic, 2nd gen. and the result is always the same. worse mpg in the rain.

[Hitech]

Even at 60 mph you are "pumping" several thousand gallons an hour of water with your tires, that takes quite a few HP to accomplish.

[Moviemike]

Originally Posted by Hitech

Even at 60 mph you are "pumping" several thousand gallons an hour of water with your tires, that takes quite a few HP to accomplish.

You bet! Water on the roads is a real big factor in reducing my mpg.

It rains here alot and during "sun breaks" when the roads dry out I can really see a big reduction in roll resistence, and an imporvement of as much as 5 mpg (on the MID).