Si, you have a history of writing knowledgeable and well reasoned posts on the forum here. I, for one, enjoy your well thought replies and witty responses.
On this occassion however, I think you need to re-think what you've put.
A few facts which contradict your post:
1. Oil does not drain back into the sump - unless stood for many weeks, possibly months.
[A worn oil pump could allow this to happen though]
2. The oil pressure regulator takes care of start up pressure. Usually, in my Z for example, the pressure within a couple of seconds of start up will sit at 120psi until the oil starts to warm and thins a little (10W40 Mobil 1) - regardless of RPM.
[The regulator, if worn, could, depending on design, reduce this higher cold-starting pressure]
3. If you've got the right oil for the operating climate - cold oil is just as effective as warm oil. It's the oil pump which might have trouble pumping a sufficient amount of 'thicker' oil if you demanded it - e.g. taking your engine above 4K RPM.
4. Most engine damage occurs within the first few seconds - whilst the pressure comes up from 0. This is one of the few times metal-on-metal contact could happen. On a regularly driven car with good oil - it should be of no concern.
Excessive idlling will cause however:
- A build up of glaze in the bores
- Excessive carbon buildup in the heads.
Anyway, Si, I know we haven't spoken before, so please don't take it personally that I'm disputing your opinion. Like I said above, I usually enjoy reading your posts and replies, but felt this particular post of yours was more mis-information than information.
Constructive criticism welcome
Simon.
