Cold weather MPG

[clarksongli]

So i've always got between 15 and 17 mpg during the warm months, but it never really ever got cold here in CT until this winter. There have been days below zero, which while unheard of, is somewhat unusual for the lower portions of CT.

Anyways, what have you guys seen your MPG drop to with the cold weather? The CTT is my daily, so i leave it outside....cold starts, plus i have a ski rack on now.

I see 13-14mpg. Unfortunately my commute is generally stop and go on the highway, so i never really get to see what it goes up to. Does this seam reasonable? I've always found it hard to believe that 15mpg is the EPA city rating, but maybe my CTT isn't running correct and getting bad MPG?

[Stephtell]

Mine's thirstier than a camel in the dessert....

I can imagine it get's worse in the cold as cold air is denser, contains more oxygen so it could inject more fuell?

You should notice extra urgency as well since the intercoolers work more efficiently in cold weather.

[clarksongli]

Mine's thirstier than a camel in the dessert....

I can imagine it get's worse in the cold as cold air is denser, contains more oxygen so it could inject more fuell?

You should notice extra urgency as well since the intercoolers work more efficiently in cold weather.

Thanks, but i'm not really concerns about the air density or dT of the exchangers.

The issue in cold weather is the car runs open loop fuel control for longer until the engine reaches temp. Compounded, we tend to let our cars run longer in idle in the morning to warm the car up before we get in. Finally, ATF becomes sluggish, and you will notice that the converter will let the transmission slip more at the cold extreme.

Add all of that up, you got a car that runs less mpg than if the car was running on a spring day. my question is, how much worse are people seeing? for me it seems like several MPG....

For a 40MPG car, i wouldn't even think twice, but does that linear drop in MPG translate into a 17MPG V8? it seems like it does for me, just wanted to see if i'm the normal....or abnormal.

[Stephtell]

Well I never let the car idle before I get in, they've invented heated steering wheels and heated seats to combat the cold...

[Pkscheldt]

Had a CTT for several years here in Mn. When temps got to 0 F and below I would see a minimum of 20% drop off in MPG, and all kinds of other issues some of which you mentioned that you never see in the "spring." A barely dirty MAF(s) or Throttle Body that would cause no issues above 0 would cause problems at low temps. A short warm up was also really helpful for the AT and Fluid etc, otherwise that temp related first gear start was annoying as ....

[White987S]

Put more air in your tires. This is eating your gas as the temps drop. Figure 1 PSI change per 10 degrees of temp change (assuming dry air).

[RacerX5]

All the above items make sense, and I would probably add that snow tires probably add a lot of rolling resistant as well, (something you'd be smart to use if you live in CT). But probably the biggest factor in reducing gas mileage BY FAR in wintertime, is that in the Northeast, they add ethanol to all gas station fuels during the winter months. Ethanol basically sucks for a lot of reasons; lower gas mileage without reduced cost, and it can do all sorts of expensive damage to the fuel systems of cars not designed for E85. Big brother claims it won't harm a thing...but that's a massive lie. It can certainly take a 10-15% bite out of fuel economy.

Now if you had a flex fuel vehicle that was tuned to run on exclusively E85 , you can get quite good performance...but still with reduced gas mileage. I have no idea how the CTT computer reacts to the ethanol in the fuel. Due to the anti-knock properties, it might be delivering a little higher power, (more advance, different mixture, etc); which will also burn more gas.

[White987S]

All the above items make sense, and I would probably add that snow tires probably add a lot of rolling resistant as well, (something you'd be smart to use if you live in CT). But probably the biggest factor in reducing gas mileage BY FAR in wintertime, is that in the Northeast, they add ethanol to all gas station fuels during the winter months. Ethanol basically sucks for a lot of reasons; lower gas mileage without reduced cost, and it can do all sorts of expensive damage to the fuel systems of cars not designed for E85. Big brother claims it won't harm a thing...but that's a massive lie. It can certainly take a 10-15% bite out of fuel economy.

Now if you had a flex fuel vehicle that was tuned to run on exclusively E85 , you can get quite good performance...but still with reduced gas mileage. I have no idea how the CTT computer reacts to the ethanol in the fuel. Due to the anti-knock properties, it might be delivering a little higher power, (more advance, different mixture, etc); which will also burn more gas.

There is ethanol in all gas, all the time, not just winter months. But, I agree with you, ethanol yeilds lower MPG's, for sure.

I have an enthanol test kit for fuels. When I was testing my gas, I saw ranges from 4% ethanol to 9% all year long. No real rhyme or reason.

[JFP in PA]

All the above items make sense, and I would probably add that snow tires probably add a lot of rolling resistant as well, (something you'd be smart to use if you live in CT). But probably the biggest factor in reducing gas mileage BY FAR in wintertime, is that in the Northeast, they add ethanol to all gas station fuels during the winter months. Ethanol basically sucks for a lot of reasons; lower gas mileage without reduced cost, and it can do all sorts of expensive damage to the fuel systems of cars not designed for E85. Big brother claims it won't harm a thing...but that's a massive lie. It can certainly take a 10-15% bite out of fuel economy.

Now if you had a flex fuel vehicle that was tuned to run on exclusively E85 , you can get quite good performance...but still with reduced gas mileage. I have no idea how the CTT computer reacts to the ethanol in the fuel. Due to the anti-knock properties, it might be delivering a little higher power, (more advance, different mixture, etc); which will also burn more gas.

There is ethanol in all gas, all the time, not just winter months. But, I agree with you, ethanol yeilds lower MPG's, for sure.

I have an enthanol test kit for fuels. When I was testing my gas, I saw ranges from 4% ethanol to 9% all year long. No real rhyme or reason.

Ethanol is roughly 33% lower in heat content (BTU) than gas, so you will get both less power and lower mileage as the alcohol content rises in mixed fuels.

[mcmike27]

The fuel changes in the winter months and is refined differently to conform to emmision standards they normally switch over to the winter blend around Oct and then switch back to the summer blend around late Feb early March. I have been seeing this drop in MPG in our Boxster ever since we acquired it an have been driving it year round in central Pa. I asked one of our local excellent idies about it and he brought up the change in the mixes based on seasonal usage. Sure enough when the summer blend comes out my MPG goes right back to the the normal level.

[JFP in PA]

The fuel changes in the winter months and is refined differently to conform to emmision standards they normally switch over to the winter blend around Oct and then switch back to the summer blend around late Feb early March. I have been seeing this drop in MPG in our Boxster ever since we acquired it an have been driving it year round in central Pa. I asked one of our local excellent idies about it and he brought up the change in the mixes based on seasonal usage. Sure enough when the summer blend comes out my MPG goes right back to the the normal level.

+1, also a very valid point. Gas blenders add more low temp volatiles in the winter to aid very cold weather starting, which will degrade MPG as well.

[RacerX5]

All the above items make sense, and I would probably add that snow tires probably add a lot of rolling resistant as well, (something you'd be smart to use if you live in CT). But probably the biggest factor in reducing gas mileage BY FAR in wintertime, is that in the Northeast, they add ethanol to all gas station fuels during the winter months. Ethanol basically sucks for a lot of reasons; lower gas mileage without reduced cost, and it can do all sorts of expensive damage to the fuel systems of cars not designed for E85. Big brother claims it won't harm a thing...but that's a massive lie. It can certainly take a 10-15% bite out of fuel economy.

Now if you had a flex fuel vehicle that was tuned to run on exclusively E85 , you can get quite good performance...but still with reduced gas mileage. I have no idea how the CTT computer reacts to the ethanol in the fuel. Due to the anti-knock properties, it might be delivering a little higher power, (more advance, different mixture, etc); which will also burn more gas.

There is ethanol in all gas, all the time, not just winter months. But, I agree with you, ethanol yeilds lower MPG's, for sure.

I have an enthanol test kit for fuels. When I was testing my gas, I saw ranges from 4% ethanol to 9% all year long. No real rhyme or reason.

Ethanol is roughly 33% lower in heat content (BTU) than gas, so you will get both less power and lower mileage as the alcohol content rises in mixed fuels.

I always thought they upped the ethanol content in the winter.

[Pkscheldt]

I am by no means a chemical engineer, but a few of my clients own service/gas stations and I've been told that the ethanol level doesn't change in the winter here in MN. I have been told that butane is added to the gasoline here in winter after september, reducing the "efficiency" of the gasoline 2-8%.

[JFP in PA]

I am by no means a chemical engineer, but a few of my clients own service/gas stations and I've been told that the ethanol level doesn't change in the winter here in MN. I have been told that butane is added to the gasoline here in winter after september, reducing the "efficiency" of the gasoline 2-8%.

Because the ethanol is blended in at the last min. with other additives as it is being loaded into the truck for shipment, the alcohol level can bounce around quite a bit (hey, they ain't stupid, they don't want gas with ethanol sitting around in their tanks, just in yours :eek: ). But in any case, when isn't it winter in Minnesota :thumbup: