Weather cool & rainy - mpg drops?

[mwr]

My first two full tanks of gas driven all by me got 45 mpg actual, 47 mpg on the car computer. Then the weather turned from dry and 60s-70s to rainy and low to mid 50s. The mpg on the car computer for this period seems to be about 43, 4 mpg less. Is that to be expected?

[corncobs]

Yes just the additional drag of the wet pavement plus the colder temps. Most likely you have the heater set to auto which will make the engine run to provide heat at start.

 

Currently I'm happy when I see 45 MPG and just hoping to keep my 44+ avg. over winter. :)

[Waldo]

Don't think of it as 4mpg, think of it as 8%. My MKT has dropped about 10% in the last month and my old Focus would also consistently drop 10% in the winter.

[mwr]

I agree about the %. But it's not really cold here, only cooler than before (and rainy).

[mwr]

Rain stopped today and I drive over 100 miles, almost 1/2 at 70 mpg, the rest at 50-60 or below. Car computer shows 46 mpg, so it seems to me that rain has a lot to do with lower gas mileage.

[corncobs]

Rain stopped today and I drive over 100 miles, almost 1/2 at 70 mpg, the rest at 50-60 or below. Car computer shows 46 mpg, so it seems to me that rain has a lot to do with lower gas mileage.

Unfortunately it does and as you can see more like you would imagine.

 

I just had a similar trip (100 miles cold and wet) and I barely made it to 41 MPG.

[mwr]

Unfortunately it does and as you can see more like you would imagine.

 

I just had a similar trip (100 miles cold and wet) and I barely made it to 41 MPG.

How fast did you drive? Is that 41 mpg actual or car computer?

[Waldo]

Think about how much spray you get from tires driving in the rain. The energy to lift up all that water has to come from somewhere.

[corncobs]

How fast did you drive? Is that 41 mpg actual or car computer?

It was very similar to yours. 68 MPH for the most part 50-55 MPH for some and very little below that.

 

41 MPG was car computer. I had to fill up in between and that gas station was weird I filled almost 2 gal more into the tank than I had used per trip computer.

[lolder]

My first two full tanks of gas driven all by me got 45 mpg actual, 47 mpg on the car computer. Then the weather turned from dry and 60s-70s to rainy and low to mid 50s. The mpg on the car computer for this period seems to be about 43, 4 mpg less. Is that to be expected?

You lose 2 mpg per 10 º F. temperature drop, 3 mpg per 10 mph headwind at highway speeds and up to 10 mpg in heavy rain. These are often cumulative ! Winter's a B---- !

Edited December 19, 2014 by lolder

[Hybrider]

You lose 2 mpg per 10 º F. temperature drop,...

 

This is so not true when the outside temp starts at 115°. The MPGs actually go up when the temp drops 10° from those types of temps. ;)

 

BTW, my experience is the optimum temp for MPGs is somewhere between 50°-70°.

[corncobs]

Your MPG pattern is just reversed. You see your beat mileage in winter that's where other see their worst. Enjoy your higher FE #

[GrySql]

 

This is so not true when the outside temp starts at 115°. The MPGs actually go up when the temp drops 10° from those types of temps. ;)

 

BTW, my experience is the optimum temp for MPGs is somewhere between 50°-70°.

This ^^^^

 

I was just in Litchfield Park (PHX) visiting a daughter/family and my mpg's were up because the weather is optimal for the FFH right now. The citrus trees all had fruit on them with the perfect weather, six months from now - not so much.