anewbie

I have my car of a couple of years, but I don't remember in the past, the gas mileage drop 10% in the winter. Perhaps, I didn't pay that much attention. But is there any logical explanation on lower outside temperature would cause the car to use up more fuel? Thanks!

MB4tronic

Tracking..

I will say however.. I've been told to fill up at night when its cold as you will get more volume of gas.. or something along those lines... maybe someone else can fill in the gaps.

Gersh320

I drop every year once it gets near freezing or below. I'm talking from 29 to 31 in summer to, as of yesterday, about 25! I'm using C and liters/100km. It was -10C yesterday morning and I burned 9.1L / 100 Km. Last fill up I traveled 90% hwy @ 65mph cruise set and only managed 8.8l/100 or about 26.5mpg.
I also fill up in the early morning because it is when the fuel is at its coolest from cooling off all night. This really only matters a tiny bit and during the summer. Doubt it warms very much right now no matter what time of day it is.

Davel

i was told winter blend gas causes a drop in mpg's...

NorseWagon

Colder air gives ya more HP due to density and if you did not adjust the tire pressure, the tires will loose volume and create more the drag.

brm

Good grief, Charlie Brown. It's colder. The air is denser. The ECU therefore feeds more gas to the injectors to maintain the proper stoichiometric ratio (a function formerly performed by the archaic device known as a choke). It also takes the car longer to warm up, and the gas used in the winter is modified and gives less power, therefore requiring more to travel a given distance.

jbec.keane

My experience is that it is not linked to the cold weather, but rather to the winter blend of gasoline used between October and April. I also see about a 10% drop in mileage.

I'm sure there is a temperature component as well as a behavioral component as we let the car warm up a little longer, but the gas blend is the real issue since it is not very cold in October or April and there is an immediate decrease in mileage.

JK

Ichabod

1. no one has yet mentioned the thickening of the lubricants in the drive train, especially the differential(s) -- not such a big factor if you use all synthetics, nowadays, but really important way back when.

2. this filling when the gas is cold trick is irrelevant -- the tanks are buried deep in the ground nowadays, not standing on stilts alongside the pumps, and down where they are the temperature just doesn't change that much, except in the far North.

KEY08

It's definately the winter blend. 10% drop is normal.

Shadow5501

It's also because it takes the engine longer to reach normal operating temperature when the weather is colder. The car burns more fuel until the engine reaches normal temp, the aforementioned electronic equivalent of a choke. So you are driving more of your normal commute with the "choke" on, resulting in lower miles per gallon.

Always looking for ways to entertain myself, I tried turnining off the heater in my 210 chassis E320 until the engine reached normal operating temperature. This would allow the engine to warm up sooner, because heat was not transferred from the engine coolant to the cabin of the car. I wanted to see if this affected the reported MPG on my 7 mile suburban commute to the office. It seemed to make a small positive difference - 0.2 or 0.3 MPG increase. Of course, I got tired of having cold feet, so I did not continue this practice...

Gersh320

I only let idle till the RPMs drop below 1k. Usually about 20 or so seconds. Then I move very very slowly, annoying cars behind me :-). I do not let the RPMs get past 1600 till the first temperature marker lights up. Then I slowly accelerate only about 100 to 150 RPM for each of the next temperature markers that light up. Once I'm about at normal temp; usually about 5 minutes of easy driving on the HWY, I go to normal speed and turn on the heater. I've spent countless hours of research and opinions about this method being far easier on the engine than simple idle. Idle takes too long to warm engine and fluids. More damage that way.

anewbie

Actually, the question originally posed was for a general discussion - whether the car uses more fuel when outside temperature is low. Now, if we point to the winter blend of gasoline, would diesel be similar? Thanks!

WEBSRFR

Can I let you know what new car I'd like to drive in 3 years so you can buy it and drive it for 3 years before I buy it from you?

Gersh320

Thanks for noticing. Made my day. I really spend a lot of time ensuring my car runs and looks as good as new. Engine compartment looks almost as good as new, I wipe it all down every time I wash the car which is often . A few times a year I remove wheels and clean inside wheels, suspension parts, and dress the rubber and plastic parts. Its almost too much, almost.

relinuca

I think BRM has pretty much hit the major factor here.

FWIW, I had nearly identical experiences with my previous '04 Jag XJ sedan...29-31mpg hwy in summers; 25-26mpg hwy in cold weather.

During the winter months, we would migrate back to the upper Midwest for the holiday season, and I could easily note the drop in mileage as we exited the warm weather of Florida/Georgia and entered the cold environs of TN/KY/OH enroute to the Chicago area.

relinuca

anewbie

Actually, this brings up another question, I live on a slope. When I travel down the hill, at 20-30 mph, my e320 won't shift up until it reaches greater than 2000 RPMS. If I don't step on the gas, it would travel at that speed and at 2000 RPMS for a while. If I do step on the gas, it still goes above 2000, before shifting into higher gear to get up to 35-40 mph and drop the RPMS. Is there anything I can do about that? What I want is for the car to shift into higher gear before reaching 2000 RPMS, without me press in the gas pedal to increase the speed. Sport / Comfort mode didn't make any difference, neither was manually pushing the shifter to the right for up shift. Got any suggestions? Thank you!

Gersh320

That is just the way it will act until the transmission warms up.

Lancelot

The W212 (at least the CDI models) have shutters behind their grille, operated by the ECU totally not allowing any cold airflow over the engine block until normal operating temp has been reached and the thermostat is open and the radiator is heated up...

Because of this I wonder if closing ( or half closing) my grille is going to make a difference during winter...

brm

Yes. Take a look at over-the-road trucks. Many of them have shutters over the radiator that can be moved. Those of us who live where the temperatures regularly get below freezing will block the radiator with cardboard if we're not going too far and it's really cold out. The car will warm up quicker and stay warmer. Just don't forget to open the grille if you're going on a long highway run.

Ichabod

(by coolant temperature, not outside air temp.) that's why they flip back and forth from one message to another (not by the driver pulling a knob just for the fun of it) while the truck is sailing down the interstate and this has a big advantage in allowing full coolant flow all the time to keep the block and head temperatures as even as possible. Actually, Lancia cars used the same system instead of a coolant flow thermostat until about 1965. My Lancia Fulvia coupe was a 1966, so it had a regular coolant flow thermostat, but my owner's manual still explained how to service the shutter type.

Gersh320

I don't know about you guys, but my little W211 has shutters on the bottom of the bumper. The entire bottom opening closes when its cold, don't know how cold it has to be to operate it but I've seen it many a cold days closed. Its really cool.