On Thu, 19 Nov 2020 16:45:59 +0000, Chris Green wrote:

Over the years they have been gradually "leaking" some black oil
which we periodically clean off.

Just normal accumlation of wear and dust mixed with whatever has been
used to lubricate the hinge in the past.

I think some sort of spray grease should do the trick, just
squirt it
at the hinge joints. It'll work its way in OK.

Or 3-in-1 spray directed using the straw

I think hinges need something a bit 'stickier' than 3-in-1 though.

I tend to agree that a thin smear of grease actually applied to the
bearing suraces/hinge pin and reasembled would be good but I don't
think anything outside will find it's way in. And the stuff left on
the outside is messy and not doing anything...

I reach for a big screwdriver and oil pen. Use big screwdriver as a
stethoscope to find the offending hinge and apply the tinest drop of
oil to the joints of said hinge letting capillary action draw it
between the bearing faces. Work the door a bit, leave for 10 mins,
check squeak has gone.

--
Cheers
Dave.