CAFE standards, do they include New England winters?

This was my first winter driving a Subaru and I was amazed at the drop in fuel economy. I went from 30-32 MPG down to 26. I could almost measure the outside temperature by looking at my MPG gage.

I realize I have 3 differentials, 8 CV joints, 4 sets of wheel bearings and a transmission all with lubricant that stiffens up at low temperatures. But there has to be a better solution. Perhaps better lubricants, perhaps small heaters…

Do the CAFE standards do any testing at low temperatures? I doubt it.

Doesn’t matter what the vehicle MPG drops in winter months here in New England. There are many many factors to this.

. Winter blend gas
. Tires slipping in snow and Ice.
. Engine is less efficient when cold, and takes longer to warm up.
. Sometimes longer idling.
. Gear is much thicker and takes longer to warm up.
…and the list goes on

There really isn’t much you can do.

I don’t think that drop is really all that bad for the winter but I think the mileage ratings are more for comparison purposes than actual indicators of MPG in the field.

Darn! Our secret is out!

CAFE standards are based on very specific test protocols for the vehicles across a manufacturer’s product range. They’re an average of the mileage of all the vehicles when tested IAW strict test requirements. I’ve attached a .GOV link so you can look them up if you’d like.

They do not take driving environment into account beyond the extent to which it’s considered in the design of the test protocols.

The tests are run in a very narrow range of temperatures so they are repeatable. If you want your car to get better mileage in winter months, yes, synthetics will help. Block pre-heaters will help (warm-ups take a lot of gas and give nothing in return). Parking in a warm garage will help. None of these will give you the same mileage you had when warm. Welcome to the real world.

That’s a perfectly normal drop in mileage for winter. It is what it is. For what it’s worth I’ve never owned a vehicle that got more than 18 MPG overall. 26 MPG is pretty thrifty in my book. I wouldn’t complain.

But I’m getting 30-32 now (thanks to the CVT). Yes I realize it is normal to drop in the winter, but a Subaru (my opinion) is hit harder than a FWD vehicle due to the reasons I mentioned. And CAFE does not take that into account.

Be interesting to calculate how many millions of gallons are lost each winter for this reason. For me it’s (6000 miles / 30 mpg) – (6000 /26) or 30 gal. Multiply by number of cars to get …

Now if CAFE did take winter driving into account, I wonder how quickly the engineers would come up with improvements in cold weather MPG ?


I guess the engineers don’t take extreme cold into consideration for one important factor. Most people in frigid temperatures let their cars idle to warm up before they drive them. A minute or two is all that’s needed but people want a toasty warm car to drive so they kill any hopes of good mpg by idling away any savings that are possible.

CAFE standards are never intended to indicate the actual mileage that all drivers should expect. they are comparative between vehicles indicating the relative mileage and are not exact If you have awd, yes, there may be a slightly greater penalty for cold weather, just like there would be for stop and go driving. Tire pressure and using winter tires is also a significant decider on mileage penalty you may suffer during the winter time. ALL cars do change and some may be worse then others. AWD and 4WD will definitely take a bigger hit. Rather then obsess about my awd and 4wd mileages. I just don’t take them in the winter when everything like longer idling times for heat and other driving habit changes can just make the comparison worthless. 26 mpg average in the winter for awd is OUTSTANDING. Wife’s Venza can drop the average from 25 to 19 in the winter months with all the inherrant affects of winter time weather. My truck drops from 20 average to 15…I pay more attention to my heating bill then gas mileage in the winter as the number of variables that can affect it increases too.

There will be no change in how engineers view them as there are too many winter time factors.

And CAFE does not take that into account.

How can it? There are too many variables. You have temp swings in this country from -40 up to 120. So it picks an average. The Cafe’ numbers are NOT to be used to determine what your gas mileage will be…but a comparison to be used against other vehicles.

How does that Subaru stack up against other vehicles in CAFE fuel mileage? If all cars were retested for Minot ND weather wouldn’t the relative position of each car on the mileage scale remain the same. As @Mike said, the figures are relative.

Ram advertises a truck with 30 mpg mileage but I seriously doubt that it will outclass that Sube in a race up the AlCan highway in January.

If the CAFE numbers are good average estimates, that means they’ll be too high half the time. The folks that get better than CAFE don’t complain.

Rod, they are relative at normal temperatures. At very cold temps, they will not have the same relationship. AWD will have a larger drop than RWD or FWD. The actual design of the differentials and any universal or CV joints is also a variable.

I can see a subaru getting 30 MPG at normal temps, and a small RWD vehicle the same, and at cold, the sub would drop to 26 and the RWD one to 28, twice the delta.


Car makes test cars at -40 in places most people don’t live precisely because SOME people DO live there. They test all the systems that matter to those folks. Does it start after a -40 cold soak? How fast does it warm up? Do the grease boots split? Does the thing drive with all that thick oil and grease? Do the plastic interior parts shatter. Does the ABS work, does the ESC and traction control keep you out of the snowbank. Stuff like that. They note mpg’s (not CAFE) and battery recovery and a myriad of other things on the data aq boxes to analyze later in a warm office.

The key points are; does it start, run and not break at -40?

Over the years, the average CCA of batteries has been creeping up because of the electronics in cars and trucks My intermediate trucks with sixes, have over 700 CCA. They start at -30 like it is summer time. ( exaggeration). So, newer cars are so homogenized to weather conditons, both hot and cold, everyone benefits. But, cold weather kills rwd, 4’wd and AWD with separate drive components far away from the heat source, the engine.

@BillRussell Too your point though; AWD and rwd trucks and cars can still drive decently in cold weather but none that I have owned has ever run as well or been as economical in so short a time as a fwd compact with transmission and front differential all next to the heat source. AWD transfer case and center differential and rear all warm up on their own through friction. An idling fwd car car start running with very little drag with a minimal amount of warm up time without moving…an AWD car can’t. It will never be as economical to drive in cold weather Till different technology becomes available.

degosa: yes, my previous car was a Passat, and I saw little difference in winter MPG. For my new forester, I swear it feels almost like the brakes are stuck on those –10ºF mornings. (small exaggeration).


It’s also worth keeping in mind that the mileage numbers that are used for the CAFE requirements that automakers have to meet are not the numbers you currently see on window stickers and in ads. Instead CAFE is based on the old EPA test cycle in use a good many years ago that are always quite a bit higher. The EPA bumped down the combined numbers across the board years ago before completely redesigning the test circuit to include more stops and starts and some air conditioning use. This gives numbers closer to what people actually see. All of these are done on a dynamometer at a fixed temperature so they don’t account for loss of gas mileage at colder temperatures. As they say, YMMV.

Am I crazy or is everyone using the CAFE numbers and the EPA miles=per-gallon numbers interchangeably? CAFE numbers are an average across a manufacturers models. EPA MPG numbers are vehicle-specific mileage estimates. Both are based on the same testing, but they’re different things.

There, I feel better now. I’ll sleep better tonight.

Oh yes, fuel economy goes way down in winter cold. My local driving goes from 22 to 18 in the winter. I lose a lot idling in parking lots waiting for my wife to do the shopping. I can’t walk on snow and ice or in high winds.

I lose a lot these days simply because I don’t drive as much. My stores are all exactly one mile away, and I no longer drive to work, to I often let the car idle in the winter until it reaches full operating temp. Sometimes I go for a short drive just to be sure the battery stays charged and the system free of unnecessary moisture.