Winter fuel mpg

[jmoser]

I noticed my mpg dropped 2.5 mpg in October - this is probably the onset of the oxygenated winter fuel in the upper Midwest.

Anyone else monitor this?

[billr99]

I noticed my mpg dropped 2.5 mpg in October - this is probably the onset of the oxygenated winter fuel in the upper Midwest.

Anyone else monitor this?

No, probably about right. When I lived in Ohio (left 12 years ago), I would see a similar drop in my Volvos, as well as a Porsche 924S I had. My Land Rover dropped too, but it was already such crap mileage it didn't really drop that much in comparison to normal.

Cheers,

Bill

[budrichard]

Happens every year to me.-Dick

[jstaneff]

Agreed. It's become a rite of Winter that gas mileage drops considerably in the colder months. Doesn't matter what kind of car.

I've also noticed that when I don't drive a car for a week or so in Winter, the mileage gets even worse. If I use a tank up within a few days, it's not too bad, but waiting a week in the middle gives substantially worse mileage; almost like the ethanol is evaporating from the tank.

[tgwillard]

Yes, both for my XC70 and the wife's S80. Mileage drops about 4 mpg in both vehicles as soon as the temperature gets into the 40's.

[Aviator]

Cold temps cause mileage drops in all cars or, whatever you're driving. Does anyone really expect mileage to go up?????

Dave.

[jmoser]

Racers will tell you that cool dry air is much much better for power since the air is denser and you get more in the cylinder - same would apply for mpg. Does not apply of course to short trips where cold starts and warm ups eat up your efficiency but on the highway yes - colder air should be better for engine efficiency than hot, moist, summer air.

[Aviator]

Racers will tell you that cool dry air is much much better for power since the air is denser and you get more in the cylinder - same would apply for mpg. Does not apply of course to short trips where cold starts and warm ups eat up your efficiency but on the highway yes - colder air should be better for engine efficiency than hot, moist, summer air.

Think about what you just said, and then think 14.7:1. I understand what you are saying about power but that's at the expense of more fuel, right? Why do you think airplanes fly at high altitudes, and those with piston engines must have the fuel leaned out the higher they go? It's to lower fuel consumption due to the thinning of air and to preserve a correct mixture/ratio of air to fuel. Otherwise you would be flooding your engine/s which would cause power loss. Everyone thinks the opposite unfortunately.

Dave.

[jmoser]

Think about what you just said, and then think 14.7:1. I understand what you are saying about power but that's at the expense of more fuel, right? Why do you think airplanes fly at high altitudes, and those with piston engines must have the fuel leaned out the higher they go? It's to lower fuel consumption due to the thinning of air and to preserve a correct mixture/ratio of air to fuel. Otherwise you would be flooding your engine/s which would cause power loss. Everyone thinks the opposite unfortunately.

Dave.

MAFs and O2 sensors correct for atmospheric and barometric variations to maintain stoichiometric A/F ratio under all conditions. Cool, dry, dense air is always optimum for peak performance whether hp or mpg.

[billr99]

Cold temps cause mileage drops in all cars or, whatever you're driving. Does anyone really expect mileage to go up?????

Dave.
Dave:

The deal in the States is that the fuel mix is changed in the Fall in most large urban centers as well as the surrounding area as designated by the EPA. Don't think they do it up here from what I've seen even in Ontario where they could use the help. The idea is that with the addition of oxygenators, the air in these areas can be kept cleaner during the colder winter months. How the chemistry works I'm not sure but in Ohio they used to mostly use ethanol as the oxygenator. The milage drop comes from the plain fact that there just isn't the same number of BTUs in a litre of ethanol as there is in pure gasoline and thus in the amount of work produced by burning that litre of fuel as translated into miles per gallon.

Cheers,

Bill

[jstaneff]

There is another smallish test. The use of Ethanol is calendar based, not temperature based. So, one week may be just like any other, temperature wise, but it may be very different fuel wise. Easy test when the mpg goes down using Ethanol fortified fuels, and up when not.

In WA state, we get 10% ethanol.

Another easy test: I have a car that can use E85. From all I know, the mpg will drop substantially if I do. So, I avoid E85.

[Aviator]

Cool, dry, dense air

And what goes along with that?? MORE FUEL!! You're not seeing the point about stoichiometric ratio. O2 sensors, air mass meters, and MAP sensors can only go so far, then the laws of physics take over....and can never be changed.

Dave.