Fuel economy worse in cold temperatures

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gj

Joined
Mar 24, 2005
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407
Location
Pulaski VA USA
2019 Mitsubishi Mirage . Current mileage is 9700 miles .
Purchased new July 2019 .
1.2 -3 cylinder . CVT Auto transmission .
I've noticed the computer read out for MPG's in the winter is about 10 to 12 MPG's worse than in summer .
Warm weather I've seen as much as 56 MPGs sometimes more . I'd say average is 42 mpg .
Since it's turn colder i rarely see the read out in the 40s .
High 20s to 35 mpg .
If there happens to be a few warm days during winter , sure enough the MPG's will be in the 40 to 50 plus MPGs. So I figure tire pressure can be ruled out .
I've read on Mirage forums this is common . Never really heard any explanation to explain it . Not the end of the world but just curious what could be wrong if anything .
Maybe common with most vehicles and I'm just now noticing it due to the technology . Appreciate any information . Thanks
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How long is your commute?

In general, it's quite normal for fuel economy to be worse in cold weather - engine takes longer to reach operating temp; air is denser; gasoline has winter additives, etc.
 
Get a whiff of your exhaust sometime on a cold start, it'll smell like raw gas coming out of the tailpipe! Add in stiffness of anything greased or lubricated, and the lower energy content of winter fuel, (and lower cold tire pressure too)- it's no surprise winter MPGs drop. Heater use before fully warming it up can hurt too, bundle up!
 
Three things can affect your mileage. 1- winter blended fuel, 2- your cars cpu adds extra fuel to make the motor run smooth and not cough , spit ,and backfire due to the cold, 3- the brand if gas you use. I know my car seems to run better on certain brands then others. Keeping your tires aired up also helps with mileage.,,,
 
It is normal to get lower fuel mileage in the winter but usually a few MPG's not 10-20 MPG's lower. Are you spending any time warming up your car before you drive?
 
Originally Posted by diyjake
It is normal to get lower fuel mileage in the winter but usually a few MPG's not 10-20 MPG's lower. Are you spending any time warming up your car before you drive?


+1 - something else is going on here if more than a few MPG difference.
 
You can turn on your air conditioner. That helps warm up the engine. The AC is now acting as a heat pump. It is taking heat out of the passenger compartment, releasing it through the condenser coil and passing it the the engines radiator. Once you begin to feel some heat turn off the AC. It works.

I had a car that had an add on AC unit under the dash. Because it was not installed at the factory I could turn on the heat and AC at the same time causing the engine to heat up rapidly.

Small efficient engines tend to warm up slower than big engines. There are just less BTU's to transfer into the cooling system.
 
Winter fuel, a richer fuel mix for a longer time when starting and until the engine starts to warm up a bit, the engine taking a longer time to reach operating temperature, all contribute to "Fuel economy worse in cold temperatures." Tire pressure drops too, quite a bit depending on how cold it gets.
 
Originally Posted by borgward
You can turn on your air conditioner. That helps warm up the engine. The AC is now acting as a heat pump. It is taking heat out of the passenger compartment, releasing it through the condenser coil and passing it the the engines radiator. Once you begin to feel some heat turn off the AC. It works.

Dear lord, only a masochist or a BITOG true believer would turn on the a/c in winter to heat the engine up faster.
Now I truly have heard it all...
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1. Cold air is more dense, so more wind resistance.
2. Cold tires are stiffer.
3. Try covering half the radiator with cardboard. Sometime cold water entering block cost efficiency.
4. Leave heater off for the first couple of minutes until temp is 150, then run fan on low speed until at full temp. You are not getting much heat anyway but running on high speed can delay warm up several miles. That small an engine might never warm up.

Rod
 
Originally Posted by gj

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Those tires look grossly underinflated.
I'd get them to a few PSI over spec.
Ride might suffer a bit, but then again, nobody buys one of those rollerskates when ride quality is of any concern.
 
Transmission fluid, auto or CVT, has a serious viscosity change from even 40C to 100C.
The extra drag inside the transaxle & final drive would add up too. : ( At least till it reaches stable temp. IF it reaches stable temp.
 
Originally Posted by Lolvoguy
Originally Posted by gj

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Those tires look grossly underinflated.
I'd get them to a few PSI over spec.
Ride might suffer a bit, but then again, nobody buys one of those rollerskates when ride quality is of any concern.


They don't look underinflated at all to me... The sidewall on the top and bottom of the tire looks equal.
 
Originally Posted by 2010Civic

They don't look underinflated at all to me... The sidewall on the top and bottom of the tire looks equal.

The fronts look especially underinflated.
This pic is also probably from months ago when nearly new (no snow/ice in pic).
 
Originally Posted by Nick1994
Calculate it by hand. I'm not sure I'd trust the computer all that much.


For sure.
That is too significant of a variation IMO to not begin serious investigation.
Cool looking little car !
 
I've owned/own two miserly cars and yes, the mpg takes a hit in the winter.

I did primarily highway; My echo (1.5) only clocked 1 tank of < 40 mpg and that was a headwind and pouring rain in the 30s.

I would calculate manually as suggested, check tires, but I would also verify the thermostat is working

If it is stuck open you will get poor heat and very bad mileage as the car is in perpetual warmup mode (running rich)
 
Same thing with my prii. Made a 280 mile highway road trip and had the same mileage hit you describe. Car was good and warmed up with tires at or a couple pounds above placard. Runs at thermostat temp of ~190.

Dense air.

You're noticing it because of the readout. Going from 30 MPG to 25 isn't as dramatic but it's about the same spread.
 
Originally Posted by Imp4
Originally Posted by borgward
You can turn on your air conditioner. That helps warm up the engine. The AC is now acting as a heat pump. It is taking heat out of the passenger compartment, releasing it through the condenser coil and passing it the the engines radiator. Once you begin to feel some heat turn off the AC. It works.

Dear lord, only a masochist or a BITOG true believer would turn on the a/c in winter to heat the engine up faster.
Now I truly have heard it all...
33.gif




Not to mention that you can dump all the heat you want into the radiator, it's not getting to the engine till the thermostat opens
crackmeup2.gif
 
Tires don't look at all underinflated.
Nevertheless, I run near max psi on mine (hybrid) for fuel economy. (I run 47.5 psi fronts and 45.5 psi rears...but on snow tires, I run 35psi)
PSI in tires may make a 2-4 mpg difference.

I agree with covering half the radiator with cardboard. See what your fuel economy does. It's worth a try and may make a big difference.

10mpg is not from Ethanol in your fuel. Might be manufacturer's fuel map (the programming in the computer) is just over-rich for cold weather. Maybe they had a reason for that (engine wouldn't run right when cold otherwise..etc) but seems like with a modern MAS (mass airflow sensor) guiding fuel delivery, you're not going to be running overly rich...even in sub-zero weather.
 
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