I should make a graph and you should read up on your cars tech at GM-volt if you want to optimize.
First off, basics, 44psi minimum, stock OEM tires only, heat at 68F eco (if you need it), preferably heated seats only until the gasser fires.
Preheat carefully (especially if you have L2 and your engine does not start) to avoid wasting lots of battery and gas off the bat.
Many volts have the wrong oil, you should use 0w30 synthetic in the winter instead of the 5w30 Dino juice many dealers slop in there.
The Volt is like the Prius and all GM products and gets epa ratings around 80F with 44psi in the tires.
You must use the stock OEM tire to get EPA MPG, any other LRR tire will drop a minimum of 3mpg, let alone snows or standard tires.
For every 10 degrees below 80F you will loose about 1mpg
This is the same as my cobalt and sadly the Buick before it.
My friends Gen iii 2013 Prius gets 28-36mpg all winter until it warms then mid 40’s.
So while I get 40 mpg at 60mph at 80F, guess what I get at 10F if I don’t drive slow?
Next,
ERDTT, you own a 2012 volt which is much more affected than later years,
ERDTT gets about 25mpg but allows/offsets heater energy use so you get more EV range, personally I hate ERDTT as it is so wasteful. I disable it and run without electric heat on my long trips to maintain 45+ EV miles and 38+ MPGcs even at -15f
You have a few options with a 2012
1. In the morning about a half hour before leaving (in cold) disable engine start and turn on the car plugged in to L1 with lights, heater (except the seat) turned off let it idle plugged in, the car should not start the engine and warm the battery then charge the battery increasing your range and gas mpg.
This can also be accomplished by setting the charge timer to have charging finish right as you leave.
Being a 2012 you might need the hold mode app to start the car plugged in without the ice firing up.
In your cars advanced settings there may be a erdtt setting which allows a cold or very cold setting (15f or 35f), depending on your heating efficiency and heat use you may gain range from one setting or the other
2. Get
https://play.google.com/store/apps/d...VoltHold&hl=en
That app, if you use electric heat (I don’t) it’s very important to instead engage hold mode once your on the highway, otherwise you loose EV range and fuel economy (a lot)
You then manually cycle into EV mode once the car is warm and use eco heat mode then on out.
.
Another tip you need to be careful with is grill block, wai and insulation
The volt does not heat up to operating temp at 20F and lower with full heat running, 170F if my thermostat is correct, if you have a means to monitor temp a grill block, WAI and optionally engine insulation help you gain back some lost economy in winter.
The volt will run on e10 or e15 regular unleaded but gains a few mpg on non ethanol Premium, Premium around here is about a buck a gallon more so I run Kwik trip 88 which is e15, I seem to do well on that gas for reasons I can’t explain.
I will post more tips but basically no new car is remotely efficient in cold weather but with the volt you have a choice to avoid using half your energy on heat if you want