Road & Track and Pop. Mechanics say differently...
http://www.roadandtrack.com/car-culture/videos/a30249/why-you-shouldnt-warm-up-your-car/
http://www.popularmechanics.com/cars/a19086/warming-up-your-car-in-the-cold-just-harms-engine/
The only time I’ve seen crankcase oil dilution in an engine in good condition was when the carb float stuck open on a generator. Automotive engines get their oil replaced long before the tiny amount of dilution becomes a significant factor.
I used to have a 1990 Ford Galaxy 500 that had a blue light on the instrument panel when the engine was below operating temperatures and instructions not to accelerate aggressively until the light went out.
Road and Track and Popular Mechanics are BOTH shills for the AlGore Church of Climate Panic-Mongering. I take their advice like I listen to Moby: not at all!
regarding warming your engine.
I noticed a bit of cognitive dissonance in those articles, as in
Warming the engine was good practice when carburetors were in use because they didn’t do as good a job vaporizing the fuel as fuel injection, the fuel droplets then washed oil off the cylinder walls.
Yet further along they say that longer idling with fuel injection can wash the oil off the cylinder walls. Which is it?
I was a mechanic for over 20 years, and did all my own servicing and repair on my vehicles as well, continuing for years after that. My experiences and work caused me to follow the practices below.
At freezing and below, I warm the car for a minimum of a minute before GENTLY driving away. Below -10, the block heater is plugged in, and the car gets at least 5 minutes. Once again, I drive away very gently until all the car’s pieces and parts have loosened up.
JMHO, YMMV