[Bob Bidonde]

Motor oil behaves like an SAE 10 in cold weather at the engine's operating temperature, so having a lower viscosity the oil will likely leak more.
Using a thermostat is an excellent practice.
In the cold winter months, condensation is a problem because of the hot and cold operation of the car's driveline. Keep the gas tank full. Run the engine several miles to vaporize moisture out of the crankcase. Short trips / idling sessions are not a good practice.