Engine temperature question

[lauda]

We all know that driving a car hard from cold is bad and I generally try to limit myself to 3,000 rpm for the first 10 minutes of any journey to give the oil time to come up to temperature.

However, I've been wondering how quickly temperature is lost once you've turned the engine off. So if I drive 10 miles to the supermarket, I'm pretty happy that the engine would be nicely up to operating temperature by the time I get there. I spend half an hour doing my shopping and come back out to the car and head off again. The water temperature gauge goes straight back up to normal operating temperature, but has the oil cooled down sufficiently in that time that I should take it easy again for the first few miles?

Or in simpler terms, what do we really mean by a 'cold' engine?

[roachcoach]

Mines does drop, but it comes up quite quickly again, usually with a half mile or so.

Caveat: I have a gauge so don't pay much heed other than the immediate eyeball, no set/accurate times/distances for me I'm afraid.

[Dr Doofenshmirtz]

lauda said:

Or in simpler terms, what do we really mean by a 'cold' engine?

Over night I would say...the oil will still be warm after a couple of hours.

But we use multi-grade oil for a reason - once the oil is fully up to operating pressure (a few seconds usually) feel free to boot it