If you ever get the urge to go operate a large piston powered aircraft sometime, here's part of the procedure for when it got chilly.
If the forecast overnight low temperature was below, say, -10 Fahrenheit, you would consider using oil dilution to aid the start the following morning. (Oil dilution is a procedure whereby avgas is added to the engine oil via a metering system to raise oil viscosity in cold temperatures.) There were two types of dilution, hot and cold. Hot dilution was when the engine oil temp was over 50*C, and cold dilution was for oil temps below 50*C. The 50*C cut-off point was because above that temperature, the added gas boiled off, while below 50*C it remained mixed with the engine oil. You carried out a hot dilution immediately prior to the last shutdown of the day. With the oil temp over 50*C, you ran the engine at 1500 RPM for thirty seconds, exercising the prop several times to allow diluted oil to the prop dome, then you shut down and waited for the oil temp to drop below 50*C. While waiting, you consulted your dilution charts and decided how many minutes of cold dilution you would need, based on the forecasted OAT next morning. If the forecasted temp was -20*F, you would need say, three minutes cold dilution. At an oil temp of say 40*C, you fired up and ran the engine at 1000 - 1200 RPM, all the while holding the oil dilution switch engaged. At the end of three minutes you shut down, holding the switch engaged until the prop stopped. Your engine was now "diluted."
The following morning, you had to burn off the dilution before take-off. This meant ground running the engine until the oil temperature had exceeded 50*C, to evaporate the gas in the system. You needed about five minutes of ground run with an oil temp greater than 50*C for each minute of cold dilution you'd given the night before. If your aircraft was equipped with a Janitrol heater, all was well. If not, it got downright frosty.
Ahh..nostalgia just ain't what it used to be.
