There was snow in the morning, which I dutifully cleared out of the driveway and off my car. But by the time I had to actually drive anywhere in the afternoon, a couple hours of light rain and sleet had (in)conveniently and thickly layered a sheet of ice over everything in sight, poor Wentworth included.
Since I was on the road to a decent two week tank of potentially 60 mpg/3.92 L/100km, I wanted to keep the streak by scraping the ice manually without running the engine. No problem, I do it all the time...
The first scrape lifted a fine spray of ice/snow/non-nomerable wintery substance off the window, but there was clearly a solid coat still below that. More scraping seemed equally futile. I eventually found a crack or two to work into, but even then it was the biggest sheet of ice I'd ever scraped on a car.
An hour and a couple cups of warm water to soften the ice later, I was off, wet, cold, and knowing full well that my Prius' ICE (internal combustion engine, not to be confused with the other stuff) does not turn off as often when there's moisture on the roads. Furthermore, the sleet kept freezing on the windshield, so any crazy defroster antics I might normally play to get the best mileage were out the window, and safety was the name of the game. So defroster and ICE running, I drove "like a normal person" through the 20 mph/32 km/h average speed limits and countless stoplights that get me to work.
I arrived with a mere 45 mpg/5.23 L/100km on the display.
This was actually not disappointing, but a couple things else:
1. Good! It's hard to remember when you can get in the 50 mpgs/4.7 L/100km without trying, and 60s/3.92 when you try, that 45/5.23 is excellent mileage for almost any other vehicle out there, especially in freezing temperatures.
2. Informative. The extent to which driving habits can affect your mileage (and thus your finances!) was not evident to me until a few months ago when I first tried the Prius. I've squeezed out 65 mpg/3.62 L/100km on this same route before, and getting 45 mpg/5.23 L/100km this time shows me how adjusting my habits, but getting there in the same amount of time yields a 44% improvement in mileage.
One other thing - on the way home, not wanting to spend an hour in the mist/rain/sleet/whatever again, I put on the defroster and started scraping. The car was on for maybe 10 minutes or so, and when I got back in the mileage for the 12 mile/19km trip was down to 36 mpg/6.52 L/100km (from 45/5.23 before)!
You can see, if the ice isn't terribly thick, and running your car in the morning before you actually drive just saves you a couple minutes in the name of convenience, or "warms it up", kick the habit. Modern cars really don't need that to save the engine, and you're getting precisely 0 miles per gallon that entire time (it sounds even worse by saying infinite L/100km!).
I also drove "normally" on the way home, since the roads were pure ice at 23°F/-5°C outside temp, save for a little gliding when I could, for a more respectable but still weather-reduced 55 mpg/5.14 L/100km.