I like my Insight's good starting reliability in the very cold weather too. It hasn't gotten to -30Celsius deg
. here this year for starting at least, but within a few degrees -26C was seen over X-mas in a stay in Sask. I've hardly ever plugged the 440w block heater even though I should if I could plan my driving times better.
fwiw: for cranking ability and any added electrical loads, my car's using a previous owner installed non-stock size 'Type 51' 12V battery rated at 550ca/450cca. It's got lots of reserve when it's kicking in the accessory starter motor below the about -10C deg. Ima battery cell temp threshold. It usually gets the Insight's engine idling quickly within a few cranks at those low temps no problem for the most part.
I did have to give the engine a bit of pedal to make it start when it was extremely cold and sitting
for a few days on occasion early on, but normally it's just turn the key and up it cranks.
Great car as it is for winters just with some cardboard and tape etc. Running the stock 0w-20 no doubt helps. When I first saw the car I took a video of the engine sound seconds after a cold start-up, [-8C] , and with the 5W-30 Castrol they ran it was a bit clattery but after a minute or two, quieter and remains about the same in spite of proper viscosity now.
Cleaning posts/connections and topping cell electrolyte levels with water was done before winter's onset and no issues in starting have occurred. Replaced a previously broken/repaired ground strap finally with a new one too.
One thing I find even in the relatively dry cold prairie air for me is fogging-up of the interior glass. It's the short city trips, stop and go, where heat doesn't build up and where visibility is an issue for me, but no more so than a lot of other vehicles in winter. I'll try open the hatch let the heated air out next time when parking to see if the windows are any clearer but it varies a bunch.
fwiw: I've altered how I operate the heater controls after start-up in the extreme cold from other vehicles because of the Insight's small displacement: I run with 'Defrost' button pushed with A/C 'Auto' on and set at Max Temp. I run that way for the first few miles recirculating cabin air, partially to get more mechanical 'load' on the engine with the A/C running, and also for dryer air glass. But after a few mins, I find switching air supply to the fresh outside source will help reduce fogging [drier source with no recirculated breathed moisture] for clearer glass. I reduce the desired cabin air temperature to about 'room temp' and switch to 'econ no a/c' once glass is clearing enough. With a few layers of cardboard in front of the radiator, plus some other warm air modifications, i find the insight can be nice and toasty enough [albeit with winter clothing] even in extreme temps running at highway speeds.
I like the Insight in cold with Mima; a way to control ima charging, put load on engine in cold to speed warmup, and as a manual form of low speed 'traction control' operated via joystick . I can see why some may put the control on the e-brake handle now perhaps for better handling in ice and snow.