Effects of weather on mpg

[PriusRos]

We all know that very cold temparatures can cause a drop in mpg.

Is it my imagination or does rain also have a noticable negative effect on mpg? Why would this be? Is it because of increased resistance on the car?

[bwilson4web]

The rain hits the car and accelerates to vehicle speed ... this takes energy. Then it falls off and takes that little bit of energy with it. The tires push stationary water away from the road, again expending energy. The windshield wipers and headlight take energy. Usually there is some wind an Murphy's law says it will always be a headwind.

Bob Wilson

[blueumbrella]

Since fall arrived I have gone from 52.5 lifetime mpg to 52.3 mpg. I expect that number to decrease even further. This will be my first winter with the Prius.

[ALS]

Just wait.

It is going to get ugly as the temperatures drop. It has been cold mid to high thirties and rainy all week and I lost 2 mpg on the last tank over three days.

So far in the last two days I'm having the worst time keeping the MPG's above 40 on this tank.

My problem is I only live three miles from work and all my trips are under five miles at the most.

This morning I had to turn the car off at the light at the bottom of my street. It had turned red as I got there. Being I know it takes close to four minutes to cycle through to me again I shut the car off. The engine in the summer has already preheated the engine but in the weather we have been having it is now taking at least a mile and a half to get up to temperature. The engine would have ran that whole four minutes while I waited.

That three miles to work which is <35 mpg and most of the distance is 25 mph. Throw in six lights and seven stop signs and yes it can get ugly if the engine is running most of the time. HEAT, what heat? Heat would kill my gas mileage as bad as the AC does in the summer.

[PriusRos]

Originally Posted by ALS

Just wait.

It is going to get ugly as the temperatures drop. It has been cold mid to high thirties and rainy all week and I lost 2 mpg on the last tank over three days.

So far in the last two days I'm having the worst time keeping the MPG's above 40 on this tank.

My problem is I only live three miles from work and all my trips are under five miles at the most.

This morning I had to turn the car off at the light at the bottom of my street. It had turned red as I got there. Being I know it takes close to four minutes to cycle through to me again I shut the car off. The engine in the summer has already preheated the engine but in the weather we have been having it is now taking at least a mile and a half to get up to temperature. The engine would have ran that whole four minutes while I waited.

That three miles to work which is <35 mpg and most of the distance is 25 mph. Throw in six lights and seven stop signs and yes it can get ugly if the engine is running most of the time. HEAT, what heat? Heat would kill my gas mileage as bad as the AC does in the summer.

Why are you turning the car off at the light??

[PriusRos]

Originally Posted by bwilson4web

The rain hits the car and accelerates to vehicle speed ... this takes energy. Then it falls off and takes that little bit of energy with it. The tires push stationary water away from the road, again expending energy. The windshield wipers and headlight take energy. Usually there is some wind an Murphy's law says it will always be a headwind.

Bob Wilson

Yeah -- makes sense.

I know there's a very significant mpg drop when it's cold. I suspect that rain also has a significant effect. Do you have any ideas regarding how much? Maybe that's one of the reasons my overall mileage has been pretty disappointing so far -- it's rained a lot since I got the car.

I am NOT looking forward to winter!

[alfon]

I also noticed a visible decrease in MPG due to rain and weather conditions. Also, I am sure some type of winterized formula is now in our gasoline here in Oregon, a madated 10% Ethonal state all year long.

In fact I can actually smell the sweet odor of the ethanol when it gets pumped into the car. Also I can smell ethanol the other day when I was at Costco in the parking lot and a car went slowly by me and the exhaust smelled sweet, indicating ethanol.

So, you got the weather, wet/snow road conditions, and winterized gasoline. You can expect a 3-8 MPG drop in MPG due to these factors.

It does appear that hybrids are really effected by these conditions more so than a 25 MPG corolla.


alfon

[ALS]

Originally Posted by PriusRos

Why are you turning the car off at the light??

Because the engine is burning fuel warming up while I'm sitting at the light. Which means zero mpg's for those few minutes waiting for the light to change.
If I'm driving at 25 mph and the engine is running at least I'm getting high thirties instead of zero mpg's with the car sitting still.

[a64pilot]

Originally Posted by ALS

Because the engine is burning fuel warming up while I'm sitting at the light. Which means zero mpg's for those few minutes waiting for the light to change.
If I'm driving at 25 mph and the engine is running at least I'm getting high thirties instead of zero mpg's with the car sitting still.

I might suggest you turn the heat off instead. If the ICE is running to generate heat for the cabin, it should stop on it's own. I believe by manually shutting down the ICE your starting over in stage 1 on re-start and that may hurt your mileage more than if you left it alone and let it's programming control ICE operation. YMMV of course.

[Shawn Clark]

Nah, turn the car off if you like. It is silly having the engine running when you aren't moving. Who cares if you restart in stage 1 with that sort of a commute? The G2's waste a lot of energy warming things up at times that you really don't want them to be warming things up.

When do I want the car to warm up? When I'm asking it to pull me away from a stop, climb a hill, etc. When do I definitely not want the ICE running? When I'm sitting at a light, running downhill, or gliding.