On Fri, 30 Aug 2013 15:12:21 +0100, GB wrote:

Certainly when we get a delivery of oil the level in the sight
tube
drops by about a cm in the 24 hours afterwards then remains
stable. I
put this down to air in the fuel that settles out.

Your suppliers presumably sell you oil by volume. Is it in their
interests to include some air in the oil deliberately?

1 cm equates to about 25 l. But most of it will get entrained during
the stiring up that occurs when the fuel falls the best part of 3'
from the fill cap to the bottom of the almost empty tank. Fill rate
is proably in the order of 400 l/min...

--
Cheers
Dave.