Effect of wet roads on efficiency: estimated 14.5% MPG drop

[Big Dave]

That rain adversely affects MPG (snow is worse) squares with my experience, but I have not found any way to avoid driving in the rain and snow.

[PaleMelanesian]

Here's an example I use:

I need to run to the store to pick up some items some time this week. If it's raining today, I can look at the weather forecast and see that tomorrow will be dry. I'll do the errand then, instead of now. Besides, it's more pleasant to be out and about in dry weather.

[Piwoslaw]

Originally Posted by PaleMelanesian

Here's an example I use:

I need to run to the store to pick up some items some time this week. If it's raining today, I can look at the weather forecast and see that tomorrow will be dry. I'll do the errand then, instead of now. Besides, it's more pleasant to be out and about in dry weather.

Sort of like what I do often, but I'm more like: It'll be dry and warm in two days, so I'll bike to town then...

[matt36415]

Although I also have no test data to add, the total mass of water moved by the tyres per mile in heavy rain must be substantial, some of it is thrown up off the road too. That all takes energy

[matt36415]

https://cumminsengines.com/uploads/d...el_economy.pdf

This is generally interesting but page 30 (check the index) has a paragraph on rain and mpg

[D.O.G.]

Originally Posted by Christ

My question is this:

Water has a lubricating effect. If the road is wet, but not wet enough for water to actually stand on the surface, needing to be moved, does this mitigate losses in FE due to rain?

I would think it would actually increase FE in this scenario, since water has the lubrication effect, which would reduce frictional losses between the tires and the road.

Thoughts?

After working in theme park maintenance departments for 20 years, I can state that roller coasters do run faster with a damp track than with a bone dry track.
That's with steel wheels, on a steel track.

Unfortunately, that scenario doesn't help us on the road.
I'm quite sure (without actual data ) other side effects of temperature, electrical load, puddles, etc, cancel out any slight gain due to reduced frictional losses.

[RedDevil]

It is the tires pumping water away and sucking it up on the back thread mainly, but also increased air resistance from droplets on the bodywork, AC to prevent fogging, lights where they would not be needed in fair weather.

I reset my Trip B counter at every cold start so I see what economy my commute yields.
My best trip in rainy conditions is about 3.7 l per 100 km.
My best in dry conditions is 3.1 l per 100 km, same route, and I have hundreds of dry commutes all beating my best wet FE.