It is worth asking "what does warm mean?"
My BMW has an oil temp gauge not a water temp one. The heater is blowing hot air long before the oil temp reaches its normal temperature. I talked to the guys at the dealership the tech guy said that only when the oil is warm is the engine properly hot.
So I played with Aldermog. The water temp gets up to 95c quite quickly but using a probe attached to the dipstick it was nearly 15 min before the oil was at the same temperature.
Conclusion: pre-driving warming up is pointless as it takes so long. An electric sump heater would be far more sensible.
I am not sure that is a good idea as pre heating the oil would change its viscosity when the engine parts would still be cold and have large gaps( tolorence) and the oil would be thinner and probably cause more wear as a result, I think.
