On Mar 24, 12:19 pm, "Edgar" wrote:
When the cylinder walls are cold acidic combustion products stay on the
cylinder wall instead of leaving as vapours with the exhaust gases and this
leads to increased wear.

This I did not know.

Idling for 5 minutes is not as good for warming up the engine as getting
some load on within, say, 2 minutes.

The manual is pretty specific. I wonder if there is a trade off that
depends somewhat on the engine involved.

The bit about 'racing' the engine after
prolonged idling is to get some fuel through the injectors as the flow at
idling is so small that the fuel in the injector can start to polymerise and
clog the holes in the nozzle.

"This is done to clean out carbon from the cylinder and the fuel
injection valve." Is what they say and I think that means what you
said.

Thanks,

-- Tom.