The biggest damage to an engine in the cold is the fact the pistons heat up before the block, taking right off and driving a cold vehicle can score the piston walls and rings, not only has the oil not circulated well enough but the close tolerance between the rings and cylinder walls are very tight when cold, this is the number one reason to allow an engine to at least be above 100? F before you start driving, My van Idles at about 5400rpm when warm, and rises to 900rpm when warm, my oil pressure is about 80psi at this time, and when warm it is about 60psi at idle, its a 4800 LR4 315 HP well built as we had 4 of them go over 200k mile in our fleet with no problems and still going as we are still using them after the company shut down, mine was the last one purchased (other then the 2007 I had that was totaled in an accident) and has 112,000 on it and even the brakes are still in good shape, I run nothing but Caster Oil 10w/30 GTX oil (in the newer vehicles, older I used 20w/50 GTX), and have never lost an engine since I started using it, 25 years ago.
Older carburetor aspirated engines had a step cam on the automatic choke which was temp controlled, that stepped up the idle to allow the engine to warm up, newer injected vehicles now use a idle by-pass control that the computer controls to do the same thing, Diesels are hard to keep heated even once they have warmed up which is why we see many of the big trucks with card board in front of their radiators or controlled louvers, also the same problem of cold starting them applies even more to them because of the high compression ratio which they have even closer tolerances between the pistons and cylinder walls, I seen a few people who bought a new pick up with a diesel and didn't know that it is a must to let them warm up before driving and it wasn't long before they had all kinds of problems with the engine, mainly blowing head gaskets and damaged rings/ cylinder walls, but if you read the operator manual it clearly points out to let them warm up before driving.