cold weather decreases mpg ?? my cruze disagrees

[6speed]

So apparently the cold weather doesnt affect the cruze mpg as much as I was expecting. Yes my overall mpg for the fall has decreased by 5 mpg which was expected. The picture below shows that in calm, gentle 30f degree weather or 95f degree weather mpg will remain consistant. Over the next couple weeks the weather in the 4-5k elevation Idaho mountains will experience 0-20f temperatures it will be interesting to see what affect this has on mpg as long as the weather remains calm and not windy.

On a side note I try to keep my tires at 38psi *cold* and is actually about where they stay while driving on the highway * warm* which is about 2-3psi less then my summer months pressure.






These mpg numbers are identical to what I see during the hot summer months on this particular stretch of highway.

I would say your Cruze actually AGREES with your “Cold Weather Decreases MPG” statement. For fall, your overall average has dropped by 5 MPG; expect to lose more during the next 3-4 months. A quick DIC snapshot you showed does not prove anything, take & post your data over time. As sciphi noted, physics changes things seasonally, especially “drawing in colder air & needing to push through colder air”. Anyone that drives the same route year round will note that. One only needs to look at all the postings in Fuelly & the graphs comparing MPG vs. month. Warm weather wins until excessive air conditioning is used. My best MPG came in August, lowest in December. Nobody can fool the laws of physics.

[NBrehm]

I'm thinking your info on the DIC may be erroneous, even if every factor remains the same just the decrease in temp will necessitate using more fuel to maintain correct AFR. Cold air = denser O2 per volume. So if the car doesn't add fuel to compensate it will run lean. There is either another factor involved or the DIC isn't accurate enough to record the change.

But figuring in warm up time, winter blend fuel and just the air fuel compensation there is literally no way you aren't using more gas in cold weather.

[Blue Angel]

Cold air = denser O2 per volume. So if the car doesn't add fuel to compensate it will run lean. There is either another factor involved or the DIC isn't accurate enough to record the change.

The engine measures the amount of air entering the throttle by detecting it's thermal mass (hot-wire mass air measures the amount of current required to maintain the wire's temperature as air flows over it). Yes, colder air is denser and therefore includes more oxygen per unit of volume, so the engine WILL use more fuel per unit of air consumed. BUT, at temperatures drop, the engine consumes less air VOLUME for a given amount of power. A/F ratio stays the same.

With a gasoline powered engine, you are not really stepping on the "gas", you are stepping on the "air", and the car's computer knows to compensate for different air temps. An engine injesting cold air is not less efficient than one injesting warm air.

[NBrehm]

Let's say for a second that you are right, I disagree to an extent, it isn't a huge number but you will use more gas due to air charge temps. and also make more HP (most of the time). But the other thing that hasn't been mentioned is friction. Cold engine fluids will consume more fuel until they hit operating temperature, which as it gets colder takes longer. The air is also denser so just driving also creates more friction, and hence more effort for the car to travel through it. Throw in days with snow and slush on top of that also require more energy to move through them. I just don't see with so many factors working against you how you could increase MPG in the winter. I lose about 5-7 MPG in my car at temps below 40, another added factor is snow tires and heavier wheels on mine but i would still expect on a 40MPG car that you would lose a minimum of 3-5MPG in cold weather.

[Blue Angel]

Cold engine fluids will consume more fuel until they hit operating temperature, which as it gets colder takes longer. The air is also denser so just driving also creates more friction, and hence more effort for the car to travel through it. Throw in days with snow and slush on top of that also require more energy to move through them. I just don't see with so many factors working against you how you could increase MPG in the winter.

All of this I agree with 100%. Cars get worse fuel economy the colder the weather gets, that's been proven over and over again. I was settled into a pretty steady rythm of keeping my avg MPG at or above 46.0 on the DIC (less when calculated), but now that the weather has dropped to below freezing temps here in Ottawa I'm having trouble keeping it above 44.5 MPG and I'm trying even harder than before. Driving like I am now in warmer weather I would expect 46.5, maybe even 47.0, so I'm making a bit of an assumption but would estimate my mileage has decreased by about 4-5% as the temps have fallen about 15 C over the past month or so.

[Sunline Fan]

Took a bit of a roadtrip this evening back to school, like I did back in October. It sure it nice to get back on campus again for a visit.

A friend just moved back from Florida and we were both going for a meeting this evening, so we met and I picked her up for ~half the trip. 140 total miles, 4.078 gallons, so 34.33. Not quite the 37.83 I got before, and it's still on Shell V-power, so the cold does have an affect on it. I did have a little higher average speed this time, 58.7. Exterior temps for the whole trip were between 24 and 28. The car was warmed up when I filled up in the beginning, so it just cooled down while we were there to have one coldish start.

For those curious, she is an RPO code WBR, but is not an installed option on the car. And I hardly think she affected mileage that much, if at all.

[mba200687]

I also agree that colder temperatures will cause lower mpg's. I have noticed in the past two weeks as the temperatures have dropped drastically from 65F to the mid 30's that my mpgs have decreased by 2-3. I also drive like grandpa going to church all the time so that’s enough proof for me.