Tim+ wrote
Steve Walker wrote

The alternators are far bigger than anything needed for
an electric fan - on my previous car, it could drive a 1kW
electric heater to speed up heating of the car, as the highly
efficient diesel was too slow to warm up in the winter!

This bit about diesels being so efficient that they
are slow to heat up a car has got to be nonsense.

We'll see...

Think about it.

Something that is clear beyond you...

ICEs turn fuel into heat and heat into motion.

Yes.

An efficient engine turns more of that fuel into motion
by generating more heat from the same volume of fuel.

But ends up with less wasted heat that can be used to
heat the vehicle than a less efficient petrol engine, stupid.

Therefore a 100 bhp petrol engine or a 100 bhp diesel
are both producing a 100bhps worth of heat,

But the diesel is getting more of it into moving the vehicle
and with less left over heating the engine, stupid.

its just that the diesel is burning less fuel to produce that heat.

Have fun explaining why diesel engines take longer to heat up.

As a consequence, power for power, efficiency *isnt* the
reason that some diesels are slow to warm up. Much more
likely its just down to the weight of cast iron in the engine.

Fraid not.