Bad gas mileage during winter?

[Doc.]

Does anybody else get bad gas mileage when its cold out? I get better mileage during summer with the a/c on. Anybody know why?

[moses0324]

^^has to do with the winter blend and also poor operating temperatures...meaning its cold out...engines have poor efficiency when its cold...efficiency increase with temperature.

[Doc.]

Do all cars do that then? My B5 was the same, but none of my previous non audi cars were this way (atleast not that i noticed). Pretty weird. But also makes sense.

[KPC1.8TQuat]

Yeah, my mileage has dropped considerably. Summer time I get about 430 miles per tank of 15 gallons, and that's without stretching it. Last week I barely got over 300. I did switch to 17" S4 rims though, which are slightly heavier than my stock 16"s.

But yes, a drop in fuel economy during winter time is completely normal.

[jaynyce]

I thought it was because of the water down gas, however i am running 19's. Here in NY we're down to about $2.03 for 93 octane, meanwhile jersey sports $1.72 for 93 octane.

[moses0324]

^^it has to do with the additive they put in the winter so fuel doesnt freeze...it somewhat reduces the octane and burn rate...this reduces efficiency.

[Kerschera4]

your engine doesn't run as efficiently when it is very cold and that is why you are getting poorer gas milage..car takes longer to warm up, oil takes longer to heat and lubricate, etc

iirc the 'winter mix summer mix' gas thing is a thing of the past

[moses0324]

iirc the 'winter mix summer mix' gas thing is a thing of the past

i disagree, more ethanol is added to gas mixtures during the winter...it has been proven...this effects burn rates

[jaynyce]

your engine doesn't run as efficiently when it is very cold and that is why you are getting poorer gas milage..car takes longer to warm up, oil takes longer to heat and lubricate, etc

iirc the 'winter mix summer mix' gas thing is a thing of the past

I notice on really cold starts my idle is at the warm up point when it starts, I believe the Rpm when my car starts in the cold is about 850rpm...

[Kerschera4]

I notice on really cold starts my idle is at the warm up point when it starts, I believe the Rpm when my car starts in the cold is about 850rpm...

yes your car will idle at the same RPM, i am talking about efficiency though.. it will idle at that point, but it takes the engine more work innitially to do so and longer to warm up to ideal functioning temperature

[sambrody44]

I'm getting like 16.5mpg...

[drmeegge]

I'm getting like 16.5mpg...

Yep me too. I range between 16 and 20. Whereas in the summer I would be getting 26-30. I have gotten around 23-25 when we have a heat wave of 40 degrees or so on the same gas.
Average temp here for the past month has been 23 degrees.

[JMRQuattro]

Cold air has more molecules per part than warm or hot air so it burns at a higher rate than warm or hot air. So there is more usable air which means it needs a higher amount of fuel into the mixture in order to burn it all. So your computer recognizes this and your injectors send more fuel to your engine to keep up with the extra air.

Although it may not technically be more air physically entering your engine, cold air is denser so it requires more fuel to burn all of it. Thus the poorer gas mileage.

EDIT: This is why you always see "cold air intakes" and stuff like that because the higher air fuel mixture you have, the more power your engine produces as well. So a bit of advice in the cold winter months... less pedal will provide you with the same amount of power that more pedal would in the summer. Adjusting the amount of pressure you put on the gas pedal during the winter is an easy gas saving technique. Because driving with the same amount of gas you normally give it will cause you to be wasting more gas. But with the small bit of added power, you can actually give it less to compensate for this effect.

[jessefrank]

http://www.fueleconomy.gov/feg/factors.shtml

...just some info that's already been stated...from a gov site.

[monkey323i]

Cold air has more molecules per part than warm or hot air so it burns at a higher rate than warm or hot air. So there is more usable air which means it needs a higher amount of fuel into the mixture in order to burn it all. So your computer recognizes this and your injectors send more fuel to your engine to keep up with the extra air.

Although it may not technically be more air physically entering your engine, cold air is denser so it requires more fuel to burn all of it. Thus the poorer gas mileage.

EDIT: This is why you always see "cold air intakes" and stuff like that because the higher air fuel mixture you have, the more power your engine produces as well. So a bit of advice in the cold winter months... less pedal will provide you with the same amount of power that more pedal would in the summer. Adjusting the amount of pressure you put on the gas pedal during the winter is an easy gas saving technique. Because driving with the same amount of gas you normally give it will cause you to be wasting more gas. But with the small bit of added power, you can actually give it less to compensate for this effect.

+1.

colder air in winter --> higher density of oxygen.
summer air --> less density of oxygen.


this is why people mod for cold-air-intake. (5hp+ while consume more gas)
computer detects the increased density and amount of oxygen and transmits singal to inject more fuel for the mixture ratio at the same time.

[47Ronin]

also has to do with tires

[yung turbo]

i just drove from to/from woodbury commons and still saw 30mpg but it did feel more powerful. Also one thing i notice; if its real cold out and the temp needle is in the middle and you put the heat fan on full blast or close to it, you can see the needle move from the middle to the cold side a little (like in between the middle line and the line before it).

[JMRQuattro]

^^ that doesn't really make that much sense. Mine doesn't do that. It should stay the same because coolant is constantly flowing in a circuit from your reservoir and into your radiator, through your engine, heater core, and some other stuff. So turning your heater on shouldn't make your engine go colder. Since coolant is always flowing through the same places regardless. Unless for some reason your heater turning on is triggering your fans by your radiator to turn on.

Does anyone else have this happen? Cause mine doesn't do it.

[gdawg'05a4]

Sounds like a faulty CTS (coolant temp sensor) if the needle is moving after it's been fully warmed up.

[47Ronin]

maybe he got his car at the outlet too ^^^ :P j/k

[Doc.]

Wheeww, thats alot of reading

Thanks for the replies guys! Makes sense now. I was just wondering since i had never noticed that in any other vehicle i've driven (mainly Hondas), so it got me a little worried

And KPC1.8TQuat, how do you manage to get 430 to a tank? Geez thats alot, lol.

[Gameinventor]

I don't agree that your engine is less efficient in cold weather. Quite the opposite. You should be able to confirm that on long trips preferably using cruise control. Factors that will lower your gas economy are short trips, snow, slush or water on the roads, driving in lower gear etc.

[davidx08]

Yeah, my mileage has dropped considerably. Summer time I get about 430 miles per tank of 15 gallons, and that's without stretching it. Last week I barely got over 300. I did switch to 17" S4 rims though, which are slightly heavier than my stock 16"s.

But yes, a drop in fuel economy during winter time is completely normal.

is that only highway driving?

[Doc.]

I don't agree that your engine is less efficient in cold weather. Quite the opposite. You should be able to confirm that on long trips preferably using cruise control. Factors that will lower your gas economy are short trips, snow, slush or water on the roads, driving in lower gear etc.

My driving schedule is pretty much the same year around. Drive to work, and back. Same distance. And every once in a while drive to store here and there.

[moses0324]

I don't agree that your engine is less efficient in cold weather. Quite the opposite. You should be able to confirm that on long trips preferably using cruise control. Factors that will lower your gas economy are short trips, snow, slush or water on the roads, driving in lower gear etc.

motors are less efficient in the cold weather!!! end of story. according to the first law of thermodynamics...

when engine temperatures increase the efficiency increases...for example: (these aren't exact numbers, just numbers used to prove my point)

engines running at 200 F = 30% efficient
engines running at 800 F = 80% efficient

so you might ask why not increase the running temps on all engines...well engine blocks, pistons, lubricant, etc...cannot deal with these extremely high temps...the intake air plays a huge part in the combustion chamber...therefore efficiency is out the window...

[northwoods]

considering cold air going into the air intake...perhaps a heater similar to a hair dryer coil would warm up the air ...or is it the additives added to the gas that also defeats better gas mileage.
Are the additives there for those that drive their gas tank down to almost empty and wonder why there is water in the gas tank? i.e. gas line antifreeze..
I drive to half tank and fill up regardless.
My gas mileage with a 2000 montana stinks...even with snow, seats, and roof rack removed. But it goes like a bat out of hell!
YOur comments on warming up the cold air intake.

[kneel]

Mine droped quite a bit but that's after i put the Thule Box on the car!

[Doc.]

Well, looks like my MPGs have dropped to ~20 now (originally was around 24-25 when I started this thread). Especially after I just changed my spark plugs (gapped at .032), and my O2 sensor in the summer. Idk if it's still the winter or what. Lol.

[PDX04a4]

ya, i usually get around 18-19 mpg in the winter. i've been getting an intermittent O2 sensor code over the last couple months so i just ordered a new front O2 sensor. also ordered some new spark plugs, its been over a year since i changed my plugs and although i got the iridium plugs i am going to try some new coppers. hopefully this gets rid of my O2 code and i get a little better performance than what i have been experiencing in the last couple months. the car feels sluggish right now.

[peteri]

Here in NY we're down to about $2.03 for 93 octane, meanwhile jersey sports $1.72 for 93 octane.

What! I paid 3.44 the other day for 92 octane.

On the freeway i get around 28 in the winter and 30+ in the summer

[Siggiepop]

mines terrible (Canada) very normal.... just commute! haha saves the most gas

[02rubya4]

I get less miles per gallon, but im not getting anything as drastic as i've been reading. on the highway i still get about 28 mpgs compared to ~30 (according to the computer) my city mileage has always been horrid at about 18 mpgs and that dropped to about 16. I'm also in this shitty rhode island winter right now so the air is pretty damn cold.

[Doc.]

ya, i usually get around 18-19 mpg in the winter. i've been getting an intermittent O2 sensor code over the last couple months so i just ordered a new front O2 sensor. also ordered some new spark plugs, its been over a year since i changed my plugs and although i got the iridium plugs i am going to try some new coppers. hopefully this gets rid of my O2 code and i get a little better performance than what i have been experiencing in the last couple months. the car feels sluggish right now.

When I first purchased my car back in '08 with 46k miles, I was getting like 26-28 city and 30-32 highway. A year later I was getting about 2-3 less for both. Now I'm getting around 20 city and 24-25 highway. No clue wtf is doing this. I'm sure there's something on the car that's affecting it.

What! I paid 3.44 the other day for 92 octane.

That was back in Jan '09

[Dresevski]

Yep me too. I range between 16 and 20. Whereas in the summer I would be getting 26-30. I have gotten around 23-25 when we have a heat wave of 40 degrees or so on the same gas.
Average temp here for the past month has been 23 degrees.

It has been a bad winter. I find myself starting when the car is cold around 12-15mpg then making it up to 20mpg on the freeway after 10 minutes at 70mph

[Doc.]

Should I clean my MAF? Would that help any?

[Doc.]

It has been a bad winter. I find myself starting when the car is cold around 12-15mpg then making it up to 20mpg on the freeway after 10 minutes at 70mph

That's pretty much exactly what mine does now.