Drastic dropoff in MPG in cold weather, rain

[gtman]

I guess this is the first car I've actually paid close attention as far as MPG's go. Two things are painfully obvious. One, this car's MPG's really drop off in cold weather (below 40 degrees). For example, today on my commute that usually shows me at around 41-42 MPG I only got 34. Maybe it's the winter blend gas playing a part in this but it's clear the turbo doesn't do well (mileage-wise) when it's cold.

The other thing I've noticed is that the mileage on the car goes down big time in rain. I don't know how much of that is the crap Firestones or just the fact mileage goes down in rain and I never paid attention.

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[Rickmeister 48]

I guess this is the first car I've actually paid close attention as far as MPG's go. Two things are painfully obvious. One, this car's MPG's really drop off in extremely cold weather. For example today on my commute that usually shows me at around 41-42 MPG I only got 34. Maybe it's the winter blend gas playing a part in this but it's clear the turbo doesn't do well (mileage-wise) when it's cold.

The other thing I've noticed is that the mileage on the car goes down big time in rain. I don't know how much of that is the crap Firestones or just the fact mileage goes down in rain and I never paid attention.

I'm not too far away from you, it hasn't been extremely cold here but today its supposed to get down to 20°. I haven't noticed to much of a drop in my gas mileage, like you this is the first car I've actually paid attention.
I've actually seen drops more so all the time, or on a consistent basis, with nothing to do with the weather. I don't know if thats coming across and making sense, but say in one week I make the same trip three times. Same exact way etc. Once ill get 37 mpg, then 47, then 28
So I'm all over the place and I can't figure it out.

 

[sadsushi]

I've noticed a drop in MPG's as well as it's got colder..my driving patterns haven't changed..right now on this tank it's just 28 mpg with about 90 miles left on the range..highs have been in the 50's lately and lows in the 20's..disappointing right now but just will have to deal with it

 

[Green82]

best i seen my avg MPG is 29 so far but the reader shows 40+ at times but either way im happy with it since my last car only got 10 MPG tops

 

[kalvin126]

Gas stations around you might have switched to winter blend fuels?

 

[motoguy128]

Mine has only dropped from 45 to 42 with similar wind conditions. But the first 5 miles of my commute dropped from 33 to 29. At 15 miles its only 35 instead of 39. But after it's up to full temp, mileage doesn't drop much. I'm not noticing a significant difference running E10 87 octane vs. no-ethanol. 87. But haven't tracked it that close and too many other weather variables anyway.

Biggest hit to mileage is because you literally must heat the entire engine block, coolant, radiator, oil and to some extent the transmission will absorb a lot of heat. You probably have a little over 400lbs of metal and fluids (water holds almost 5x more heat per lb that aluminum and 2.5x oil).

I didn;t check specifications, but for an easy calculation, lets say 10lbs of water in the block and 400lbs of aluminum and oil, that's approx. 94 btu/F temp rise. We need to raise it about 300F on average (around 180F for coolant, but engine block I think runs closer to 500F. So lets say a 100F temp rise to the point where coolant needs to cool the block. So that's 9,400BTU. Doesn't sound like a lot, but gasoline only has 114,000 BTU/gallon. (Which is interesting because natural gas costs about than 1/2 that of gasoline per BTU) . So you could consume maybe around a 1/10th of a gallon the first 10 minutes of driving.

Plus, in cold weather, air is more dense and wind resistance increases a little.

Also, Catalytic converter also needs to be a minimum of 1100F and the engine runs rich to warm it up I think and the engine runs a little richer.

To make matters worse, until it's warm, it's robbing power, so you use more throttle and operate teh engine less efficiently.

 

[gtman]

That's probably my issue in the cold weather then. My commute is 9 miles and the engine probably is barely heating up when it's only 30 degrees out there.

 

[darkness975]

My last car, as well as this car, experience noticeable drop in MPG based on what the computer says when it gets cold. This is not a new phenomenon, at least not to me.

It is yet one more of a myriad of reasons I absolutely despise winter and cannot wait to move someplace warm. And with a garage.

 

[turbo lover]

If you have a block heater, plugging in for an hour or two reduces the penalty that you get from a cold start. We have cheap electricity and expensive gasoline here, so it ends up being beneficial to plug in. Maybe not in the USA where gasoline is cheaper and electricity is more expensive.

 

[julianzh]

I get free gas thru my job. Blasting the heat each morning.

 

[jgreen16]

https://www.fueleconomy.gov/feg/coldweather.shtml

 

[bembol]

Normal

 

[darkness975]

I love the articles and people that tell you not to idle it to warm it up for more than 30 seconds in the Winter. If I tried to drive to work in the morning in the Winter after the car being on for only 30 seconds I would not be able to see anything since the windows would still be all frosted up.

Never ceases to amaze me how they pretend that we all live in South Florida where temperatures below 50F are a rarity.

 

[jks]

Rain really hurts gas mileage on the highways. It takes a lot of energy to push water out of the way of the tires. Wider tires suffer more.

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