Cold weather gas mileage

[perrymk]

I track my gas mileage using Excel. I typically get 39-41. My dash computer has been reading 42. With the recent cold snap my gas mileage appears to have plummeted into the mid 30s. I estimate based on the miles remaining in tank option on the dash computer. The first half of my previous tank appeared fine, the second half went through fast. The dash computer even dropped to 41.9 after months at 42 and my last Excel measured tank was at 38.

The only change I can think of is the recent cold snap. Here in the Florida Panhandle we have been in the 20s F at night and only 40s-50s F during the day. Could that affect gas mileage so drastically? I'm anticipating this tank will be even lower than 38mpg.

 

[Swordsmith]

A) those differences are well within standard deviation

B) yes, colder weather does hurt your MPG several ways. Not sure which apply to you though.

b1) Gas blend changes. Does Florida do this? But winter gas gets worse mpg than summer gas.

b2) Warming up the car. Lots of folks turn on their car and let it idle for a while for a variety of reasons. If you aren't doing this it doesn't apply.

b3) ECU changes the fuel ratio to compensate for cold engine. Of course this only applies for a couple minutes each trip till the engine warms up... so it matters more if you do short trips rather than long ones.

b4) Cold air is denser air, giving you more available power but worse mpg.

C) It's 15 degrees out with 3 feet of snow on the ground and the plowed streets are "only" 4 inches deep. So enough already with your Florida version of "cold weather"! :banana:

 

[perrymk]

Yeah I figured someone would poke a little fun at the Florida problem of below freezing weather. I was talking to my girlfriend, a single mom, about the problems of being a lifelong bachelor. Like how the other day I was getting ready for a nap on the couch couldn't decide between laying on my right side or my left.

Thanks for the insights. The only variable I could see was the weather but didn't think it would be so drastic. It will probably be about 10-12% lower this tank, so maybe 35-36 mpg. I've gotten use to 40mpg.

I should have mentioned:
2014 Sonic hatchback LT
1.4T, 6 spd MT
29000 miles
only use ethanol free gas

 

[Maddog2020]

That sounds about right, I live in Michigan and in the Summer I get about 43, 44 MPG, but in the Winter it drops to about 36 to 38 MPG. Of course my low MPG's will last a lot longer than yours!

 

[perrymk]

Results are in. Half a tank of cold weather (Florida cold, not Fairbanks, AK cold): 38.3 mpg calculated in Excel. A full tank of mostly cold weather: 37.5mpg. It really seemed like it might have been a little less but Excel doesn't usually lie. The temperature has climbed back into the 60s and 70s F during the day, 40s to 50s a night and the gas mileage appears to be returning to normal based on the miles remaining option on the dash computer. So an 8-10% drop in mpg due to weather.