# Miles per Gallon **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** outback, fuel-economy, subaru\ **Created:** [December 15, 2010, 3:46am UTC](https://community.cartalk.com/t/miles-per-gallon/58733 "2010-12-15T03:46:49Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![bbruden](https://avatars.discourse-cdn.com/v4/letter/b/bc8723/32.png) [@bbruden](https://community.cartalk.com/u/bbruden)\ **Post date:** [December 15, 2010, 3:46am UTC](https://community.cartalk.com/t/miles-per-gallon/58733/1 "2010-12-15T03:46:49Z")
How much is a reasonable drop in mpg when old man winter sets in on my cars? ---
**Author:** ![rokgpsman](https://avatars.discourse-cdn.com/v4/letter/r/5e9695/32.png) [@rokgpsman](https://community.cartalk.com/u/rokgpsman)\ **Post date:** [December 15, 2010, 7:36am UTC](https://community.cartalk.com/t/miles-per-gallon/58733/2 "2010-12-15T07:36:39Z")
Just an opinion, I didn’t think the ambient temperature affected the mpg enough to be measured. The engines on newer cars warm up fairly soon and the air density doesn’t change that much over the typical temp range we see. If the mpg was seriously affected by the changing of seasons the government mpg ratings would have to account for this on the window sticker. ---
**Author:** ![Xebadaih](https://avatars.discourse-cdn.com/v4/letter/x/d07c76/32.png) [@Xebadaih](https://community.cartalk.com/u/Xebadaih)\ **Post date:** [December 15, 2010, 8:10am UTC](https://community.cartalk.com/t/miles-per-gallon/58733/3 "2010-12-15T08:10:00Z")
MPG is very much affected by outside temperature. If it’s 20 degrees outside your car spends much longer in open loop running rich than if it were 90 degrees outside. So temperature really makes a big difference if you make lots of short trips. Starting in 2008 the EPA started figuring ambient temperature into their mpg estimates. ---
**Author:** ![Joseph\_E\_Meehan](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/joseph_e_meehan/32/21_2.png) [@Joseph\_E\_Meehan](https://community.cartalk.com/u/Joseph_E_Meehan)\ **Post date:** [December 15, 2010, 10:49am UTC](https://community.cartalk.com/t/miles-per-gallon/58733/4 "2010-12-15T10:49:55Z")
There are a number of factors. One is the fuel. Winter blend fuels (diesel and gasoline) generally have lower energy, so you get lower mileage. That varies greatly depending on where you live. Local temperatures and more important, the length of your drives will also be a big factor. We all tend to have shorter drives during the winter. I would suggest that anything over 10% is large and less than 3% is small. These small numbers are difficult to measure accurately. ---
**Author:** ![MikeInNH](https://avatars.discourse-cdn.com/v4/letter/m/a587f6/32.png) [@MikeInNH](https://community.cartalk.com/u/MikeInNH)\ **Post date:** [December 15, 2010, 2:13pm UTC](https://community.cartalk.com/t/miles-per-gallon/58733/5 "2010-12-15T14:13:31Z")
> I didn’t think the ambient temperature affected the mpg enough to be measured. I take it you live in the South. Cold weather can have a drastic effect on mpg. I usually see a 2-3 mpg drop. If it’s snowing a lot…3-5 mpg drop. ---
**Author:** ![mark9207](https://avatars.discourse-cdn.com/v4/letter/m/71c47a/32.png) [@mark9207](https://community.cartalk.com/u/mark9207)\ **Post date:** [December 15, 2010, 4:27pm UTC](https://community.cartalk.com/t/miles-per-gallon/58733/6 "2010-12-15T16:27:57Z")
I usually see a 10-15% drop in mpg, but my car is a little over 20 years old and rather well worn. Newer cars may not be as profoundly affected, but you will see a difference if you normally keep track of things like this. I track mileage with every fillup, and when the weather is bitterly cold I may only get 270 miles out of a tank as opposed to the usual 300 in the summer. ---
**Author:** ![circuitsmith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/circuitsmith/32/40376_2.png) [@circuitsmith](https://community.cartalk.com/u/circuitsmith)\ **Post date:** [December 15, 2010, 4:52pm UTC](https://community.cartalk.com/t/miles-per-gallon/58733/7 "2010-12-15T16:52:58Z")
Cold, dense air increases wind resistance. ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [December 15, 2010, 5:36pm UTC](https://community.cartalk.com/t/miles-per-gallon/58733/8 "2010-12-15T17:36:47Z")
Typically in my 4-banger cars my mileage will drop 2-3 mpg in the winter, but it’ll vary widely depending on the vehicle, the type of driving you do, and the driving environment. My driving is mixed, but if you live in North Dakota and your driving is all local you may rarely get to full operating temp. I remember when I lived there we used to put cardboard in front of the radiators just to get the engine to warm up enough to get some warmth in the car. ---
**Author:** ![realbinky](https://avatars.discourse-cdn.com/v4/letter/r/a87d85/32.png) [@realbinky](https://community.cartalk.com/u/realbinky)\ **Post date:** [December 15, 2010, 6:37pm UTC](https://community.cartalk.com/t/miles-per-gallon/58733/9 "2010-12-15T18:37:34Z")
less energy per volume, to be precise (and anal) 🙂 ---
**Author:** ![rokgpsman](https://avatars.discourse-cdn.com/v4/letter/r/5e9695/32.png) [@rokgpsman](https://community.cartalk.com/u/rokgpsman)\ **Post date:** [December 16, 2010, 12:38pm UTC](https://community.cartalk.com/t/miles-per-gallon/58733/10 "2010-12-16T12:38:47Z")
Ooops, I stand corrected! (and yes, most of my driving has been south of the Mason-Dixon line) ---
**Author:** ![circuitsmith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/circuitsmith/32/40376_2.png) [@circuitsmith](https://community.cartalk.com/u/circuitsmith)\ **Post date:** [December 16, 2010, 3:00pm UTC](https://community.cartalk.com/t/miles-per-gallon/58733/11 "2010-12-16T15:00:24Z")
Given that absolute zero is ~ ?460?F and the ideal gas law PV=nRT, then it follows that 92?F air is 20% less dense than 0?F air, and that’s pretty significant. ---
**Author:** ![ok4450](https://avatars.discourse-cdn.com/v4/letter/o/e9bcb4/32.png) [@ok4450](https://community.cartalk.com/u/ok4450)\ **Post date:** [December 16, 2010, 5:32pm UTC](https://community.cartalk.com/t/miles-per-gallon/58733/12 "2010-12-16T17:32:52Z")
The mileage in my Lincoln has actually gone up about .7 to 1 MPG since cold weather hit. It’s averaging about 25.2 combined with an 80/20 mix of highway/city whereas before it running about 24.2 to 24.5