Effect of Rain on gas milage

[mbedit]

First, off, I have to note my C-max is still well with-in the break-in period, so this could be due to that, but typically, It had been reporting about 40 mpg ea way to/from work, approx 20 miles ea way, but coming home today it was raining pretty good, and the MPG dropped to 33. Seems like a pretty big drop for rain.

 

Is that seem normal?

[Laurel]

Well we live on the Lower Mainland of BC and officially it is a rain forest, and it really rains here and I see no decrease in mpg in the rain.  Yes, with lower temps as it takes the car longer to warm up. but not rain.  My husband ruins my excellent mileage as he is always cold and cranks up the heat LOL.

Edited February 8, 2013 by Laurel

[mbedit]

Its probably the fact that its still in the break-in period then.

[RachelnLa]

If it was raining that hard maybe your driving technique changed? I know I try more cautious in the rain.

[StoBro2]

In the rain you're more likely to have the windshield wipers, defroster and headlights on, so there will be an extra load on the system. And I have to think that propelling a car down the road has to be easier through dry air than through a heavy downpour, especially at highway speed. If the road is rutted, you could be pushing a lot of water out ahead of or to the sides of the tires, too.

[plus 3 golfer]

I recall seeing calculations of a snapshot of the amount of water in a 1 m^3 of air during a downpour of 1 inch of rain per hour. It's actually quite small like about 1cm^3 of water in a volume of 1m^3 of air. I don't believe this small amount of water will affect the density of the air very much and thus have little effect on FE. Also, remember that the more water vapor in the air, the air density decreases.

 

So, it's not the rain in the air that reduces FE during rainstorms but the tires pushing rain off the roadway. We all know how driving through puddles of water on the road slows the car down.

[Jus-A-CMax]

Slow down in the rain, go EV and save that way  :rockon: 

 

PS I suspect its the colder temps, water on the road that effected your FE. 

[MikeB]

Especially for those of us relying on the battery to provide heat, rain makes a difference. The moist air means that I have to run the climate system on defog, which means turning on heat and everything. On a dry day, many Energi drivers have no problem leaving the climate system off and just turning on a seat warmer.

[mbedit]

So, today no rain and right back to higher MPG. 38 MPG into work and 43 MPG coming back. There's also a bit of wind with rain, so I'm betting the combo of wind and drag on tires due to rain was it.

[Tdefny]

Especially for those of us relying on the battery to provide heat, rain makes a difference. The moist air means that I have to run the climate system on defog, which means turning on heat and everything. On a dry day, many Energi drivers have no problem leaving the climate system off and just turning on a seat warmer.

You run the heat?

 

I have been too much of a cheapskate to do that. I feel cheated if I don't make it all the way home on battery. I will either run the fan directed to the windshield and temperature and fan set to low or get really lazy and crack open the window a bit. As a side benefit, i found the car is less likely to fog if the heat never comes on. Also the exterior stays cold so snow doesn't freeze onto it so it is easy to clear off.

[F8L]

Rain can have a huge effect on fuel economy. Water on the road increases rolling resistance. Large amounts of water will significantly increase the amount of horsepower required to maintain a desired speed. Next time you drive through a puddle notice how quickly your car slows down. It takes a lot of energy to pump water through your tire tread and move it out of the way and/or throw it into the air. That energy came from kinetic energy which ultimately came from gasoline.

 

If you think rain has no effect on your fuel economy then I would suggest researching the subject and monitoring your mpg more closely. :)

 

http://ecomodder.com/forum/showthread.php/effect-wet-roads-efficiency-estimated-14-5-mpg-109.html

 

http://www.cleanmpg.com/forums/showthread.php?t=14422

 

http://www.foxnews.com/leisure/2012/08/03/getting-better-gas-mileage-in-warm-weather-here-why/

[ptjones]

Rain can have a huge effect on fuel economy. Water on the road increases rolling resistance. Large amounts of water will significantly increase the amount of horsepower required to maintain a desired speed. Next time you drive through a puddle notice how quickly your car slows down. It takes a lot of energy to pump water through your tire tread and move it out of the way and/or throw it into the air. That energy came from kinetic energy which ultimately came from gasoline.

 

If you think rain has no effect on your fuel economy then I would suggest researching the subject and monitoring your mpg more closely. :)

 

http://ecomodder.com/forum/showthread.php/effect-wet-roads-efficiency-estimated-14-5-mpg-109.html

 

http://www.cleanmpg.com/forums/showthread.php?t=14422

 

http://www.foxnews.com/leisure/2012/08/03/getting-better-gas-mileage-in-warm-weather-here-why/

On my long trip I had rain coming back. I went from 44mpg to 37mpg in the rain, wind and no drafting at 60mph. I hit 3-4 puddles with one tire and almost jerked steering wheel out of my hands at night Too. That will sure wake you up. I slowed down to 59mph after that and truckers still go by and destroy your visability.

[mbedit]

I was trying to understand how big a drop I should expect. Driving home today, it was drizzling, so the road was wet and sure enough, my MPG dropped from about 43 to 40, which is very believable. 

 

In regular vehicles, you just don't get the type of data the hybrids report out, so most people don't really think about it. 

[valkraider]

Rain (and humidity) also reduce the efficiency of ICE motors. Moisture doesn't burn.

 

:)