MPG in the rain

[Stratman]

Twice recently I have done motorway journeys where the outward part was in good weather and the return trip in really horrible heavy rain. On both occasions I used the cruise control to maintain a constant speed. If anything, the rainy trips were at a lower speed for safety's sake. Within experimental limits, the good weather trips gave 60mpg and the rainy returns 48mpg.

I'm guessing pumping all that water off the road surface takes a lot of energy but is it really 12mpg's worth?

 

[rf065]

If you have wide section tyres it's probably right.
Tyres are reckoned to dispel a few gallons of water per minute, that energy must come from somewhere.

Russ

 

[wemorgan]

What about the wind strength and direction?

 

[Bobby Dazzler]

I would expect it to be slightly worse in inclement weather - 25% is more than I might have imagined but not far off.

Was the traffic slowing down and then speeding up because of the weather, or did you cruise hold for long stretches?

 

[robert.saunders]

Poor weather, increased engine load? Heated windows, lights, wipers etc coupled with increased drag?

 

[A210AMG]

I don't know if its true but my dad says not to use cruise in the wet as the car can aquaplane and the skid control etc doesn't work the same on cruise?


Is that smidle widdle

 

[Stratman]

I would expect it to be slightly worse in inclement weather - 25% is more than I might have imagined but not far off.

Was the traffic slowing down and then speeding up because of the weather, or did you cruise hold for long stretches?

The CC was on for long stretches. Most sane people were at home keeping warm.


No heated windows, 195 section tyres. Lights and wipers were on, but I've done the same journeys in the dry at night and got over 60mpg.

I have had the CC on during a slight aquaplane. It dropped out and the ESP had the car pointing in the right direction before my sphincter could react

 

[Dryce]

I don't know if its true but my dad says not to use cruise in the wet as the car can aquaplane and the skid control etc doesn't work the same on cruise?

Modern cruise control systems are hooked up to the ESP system. If something bad starts to happen then cruise is disengaged automatically. ESP does its thing regardless.

However there was a discussion on the forums last year about the potential for problems where you resume CC and the car accelerates quicker than you expect in an area where there is surface water.

 

[Mactech]

My thoughts on mpg in the wet.

http://www.mbclub.co.uk/forums/showthread.php?t=46142