flanders

Starting with clutch down also ads additional wear on the thrust bearing, which is in the end could cause complete engine failure.
So I always start with clutch up and rather have my starter or battery fail

S2kTbo

flanders

It's more important if you are using a heavier pressure plate but all the small things do ad up.
Since we don't have the clutch interlock switch on our cars it's easy to choose for yourself

Nottm_S2

How could a clutch bearing, which is a wear part, cause 'complete engine failure'?

That sounds mad

My BM won't start without the clutch down.. it fooking confused me on the drive home on my first (thirst?) of many petrol station stops

flanders

Not clutch bearing, thrust bearing or thrust washer seems to be the more correct word.
When you press down your clutch it will put a load on the thrust washers, when engine is not running these washers are dry and has no lubrication.
If they fail which is not that uncommon unfortunately, the crank and block is most likely trash.
Here is a picture for better understanding

Nick Graves

If you've left it standing for months, that might be a concern.

But with modern clingy lubricants, the forces will normally be minimal at cranking speeds.

flanders

Well everyone is free to choose themselves, no load at all or something between minimal and significant.
Thrust washers does not "hold" oil like the main bearings so I after the engine has cooled down completely the wear is probably very close to the same as after months.