Do you get about 4 MPG less during winter ?

[paraganek]

After driving Yaris for just over a year I found the 4MPG difference between summer and winter quite interesting.
The thing is I live in Portland, OR and winters are very mild here, we may have 2 days in winter when temperature during a day drops bellow freezing the rest of winter we stay in 40's.
So driving in summer months I average 39MPG and driving in winter I get 35-36MPG. I only drive commuting to work = 100% heavy city traffic, no highways. I do not use A/C.
I bought 2008 Yaris LB manual in March 2008 and have been driving it since.
I have 13000 miles on it.
Is anyone experiencing the same difference between summer and winter MPG ? Would it be the cold winter starts in the morning ? Any ideas ?

Just curious

Feel free to check my Gas Log

Daniel

[staticorex]

I always get worse millage during the cold months. I was told it was an additive in American gas that is supposed to help but has the opposite effect. I'm sure others will chime in to confirm or ridicule me. :p

[AlexNet0]

I get like 32 in the winter vs constant 40's in the summer, dont know why

[justjesus]

Cold air vs warmer air. You get more power with the colder air, right? Well, with the warmer air, you get better mileage. I believe it's because it helps with atomizition. Some people do "warm air intakes" cuz of this. I keep meaning to try it myself, but I'm forgetful.. and sometimes lazy

[staticorex]

^ The only problem with that is on the dyno I ran hot air and then freezing cold air to the intake and had absolutely no change in hp. Not even a .01 difference. But the theory sounds right. Hmmm....pondering... :p

[SpaceShot]

In the northeast there is summer and winter gas formulations and it seems to add to the effect of temperature.
But the cold temperature affect doesn't require freezing temps to have a hit on your mileage. Much below 50F and I can notice that it takes much longer to get the engine to full operating temperature. Even though the cold indicator goes off around 130F (water temp via ScanGuage) the engine doesn't hit full temp until 182 or so.

Even though the winter here is colder and I get better mileage with a favorable commute, the winter effect is similar, 3-5 Mpg over the same commuting routes for all seasons.

[RS_91CAMARO]

I did as bad as 22 MPG in the winter but always warm it up before i go anywhere.

[BailOut]

I have 3 things working against me each Winter:

1) Reformulated gasoline
2) Road conditions (300-400 inches of snow each year)
3) Temperatures below 0F many mornings

I cannot get around #1 or #2 but a grille block greatly helps with #3. Without the grille block my average Winter MPG is about -5, but with the grille block it's about -3.

[nemelek]

Although you don't have "winter" in Portland, the rain and wet roads will lesson your mpg. I get about 3 mpg less during the winter.

[enkid]

I get about 8 to 10 MPG worse in the winter on average
sometimes more, sometimes less

Longer warm up time
Winter formula fuel
Rolling resistance of tires worse when cold
More wind, more rain and snow

[paraganek]

thank you guys for sharing, it makes sense to me now

[Yaris Hilton]

Originally Posted by enkid

Rolling resistance of tires worse when cold

That was impressively demonstrated by the old-fashioned nylon 6-ply bias tires I had on my 1940 Ford. When left sitting for a while, the cords would take a set and "flat spot," which would smooth out after rolling for a while. In cold weather, I'd go thumping down the road on flat spotted tires for quite a while. Modern tire cord materials don't set that dramatically, but they still stiffen up quite a bit. As do the rubbers used in the tread and carcass of the tire.

[07WYarisRS]

Almost guys .....


FI engines use more fuel in the winter because of the cooler air temps.
Cold air is more dense there for more oxygen... the engine compensates the would be lean fuel air mixture by adding more fuel.
Thats why carbed engines are adjusted and re-jetted for temp /altitude changes, thats also why racers test before the races for track conditions and ait temps/humidity etc...
Air temps play a huge roll on the F/A mixture

[TheSilkySmooth]

Originally Posted by 07WYarisRS

Almost guys .....


FI engines use more fuel in the winter because of the cooler air temps.
Cold air is more dense there for more oxygen... the engine compensates the would be lean fuel air mixture by adding more fuel.
Thats why carbed engines are adjusted and re-jetted for temp /altitude changes, thats also why racers test before the races for track conditions and ait temps/humidity etc...
Air temps play a huge roll on the F/A mixture

Sorry. Almost. After warmup, With the denser mixture you require LESS throttle opening for the same torque. So now you use less throttle and you're back to zero difference AFA air temp goes ( except during cold start enrichment) It's (1) longer warmup time due to COLD ENGINE not ambient air, (2) colder oils causing parasitic drag due to energy expended in shearing the lubricants, (3) higher drag and loss driving in snow.

extended explanation: A Heated air intake at cold start would help speed engine warmup and efficiency but generally the colder and denser the inlet air the more efficient the engine AFTER warmup. Water takes a lot of energy to heat - and your fuel is being expended in heating approx 2 gal H2O additional 40-90 degrees to Op temp in the cold winter days. There goes your fuel.
1 word - Block heater;)

[EasyDriver]

My worst mileage was in January 09.....23.76 mpg. It was really cold, snowy and my trips were mostly around town....with a little warm up time. Of course, the car only had just over 1000 miles on it too. I'm looking forward to breaking 40 mpg someday...but haven't done it yet!

[07WYarisRS]

Originally Posted by TheSilkySmooth

Sorry. Almost. After warmup, With the denser mixture you require LESS throttle opening for the same torque. So now you use less throttle and you're back to zero difference AFA air temp goes ( except during cold start enrichment) It's (1) longer warmup time due to COLD ENGINE not ambient air, (2) colder oils causing parasitic drag due to energy expended in shearing the lubricants, (3) higher drag and loss driving in snow.

extended explanation: A Heated air intake at cold start would help speed engine warmup and efficiency but generally the colder and denser the inlet air the more efficient the engine AFTER warmup. Water takes a lot of energy to heat - and your fuel is being expended in heating approx 2 gal H2O additional 40-90 degrees to Op temp in the cold winter days. There goes your fuel.
1 word - Block heater;)

Yes they run more efficiently and also make more HP when temps are colder, thats why guys love running the drag strips when the temps are just perfect, cold air temps but warm track surface is PERFECT. but running more efficiantly does not mean they use less fuel.

regardless the throttle position when the pistons travel from TDC to BDC they draw in the same amount (Volume) of air. In colder weather there is MUCH more oxygen and must be compensated by adding more fuel or the mixture will be lean..
there is no way around it.
Sure there is longer warm ups in colder weather but this is why your engine idles much higer in sub zero temps then a cold start on a hot summer morning. Even at idle when the engine is warm, the engine still uses a lot more fuel when air temps are cold because of the much higher oxygen levels.

So your sayin a HOT ENGINE, I fill up, roads are completely clear but the temps are -10 I'm nopt going to see any changes in fuel economy... BS.
Engine black and water temps are normal, oils hot, tires are hot, no snow, yet a 5 strait hour treck on the highways sees far less mileage then the same trip in the summer.
And that has nothing to do with there being more oxygen in the cold air?

Why is it then older cars with carbs, ATV's motorcycles, outboards run so lean in cold weather.

[TheSilkySmooth]

Originally Posted by 07WYarisRS

... regardless the throttle position when the pistons travel from TDC to BDC they draw in the same amount (Volume) of air.

This is completely incorrect. When the engine is throttled, at a given RPM, it is operating at a vacuum and the cyl is filled with less air mass. BTW the engine does not draw in air - there is no such thing as "sucking". You are confusing displacement with air mass. AFA mileage hits in cold weather, its almost ALL coolant warmup and gear and bearing lubricant shear. In extreme cold you will see additional losses in tyre stress heat loss and oil sump Lubricant heat loss. And dont forget your heater - the energy req'd to heat the air in the cabin.

[Yaris Hilton]

Colder, denser air can burn more fuel and generate more maximum horsepower, no question. There doesn't seem to be a simple, straightforward "one size fits all" answer for the optimal intake air temperature for best cruising fuel mileage. There are many posts with data and discussion on the fuel economy fora.