They all recommended a hot oil change. They cut through some myths and got some hard facts. The engineers were amazed by the results. Once the engine had started, it took much longer than everybody had thought for oil to reach all the parts of the valve train. The situation got worse at lower temperatures.
Some engines have balance shafts that run at twice the crankshaft speed.
The bearings on the balance shaft can suffer a lot of damage by running dry for a few minutes. A cold start can be a dry start. A cold start can also be a dirty start, because of the oil pressure-release valve in your oil filter. The crankshaft bearings usually get their oil directly from the filter, and so they usually suffer first. Reving a cold engine can send dirty oil to the crankshaft bearings.