The Mk2 Focus Haynes manual says this gearbox should be filled to the bottom of the filler plug threads. Other gearboxes I have seen in the past are also supposed to be filled to this level.

I have read some posts on here that suggest it should be around 10mm below the filler plug hole. I have never heard of this on any other gearbox.

What was Ford's reason for that?

Tbh when I filled mines it was very awkward so I filled it until it fell out and waited on it stopping dripping but you will need something under there to soak it up I cut off a piece of water hose and from the top of the engine I moved it down to the location and pushed it in then the oil I had plugged into the the hose and I filled it that way downward.

Fill to the dribble

Thanks for the replies.

I had already topped it up to the lower of the filler hole.

It took around 100ml of oil to bring it back up to level.

There is a small leak from what appears to be the mainshaft seal inside the bellhousing.

It's normally the selector seal that goes and it will get worse. This helped me when mines done it and you must get an original ford seal or it will fail.

https://workshop-manuals.com/ford/focus_1999_08.1998-12.2004/mechanical_repairs/3_powertrain/308_manual_transmission-transaxle_clutch_and_transfer_case/308-03a_manual_transmission-transaxle_vehicles_with_5-speed_manual_transmission_(ib5)/description_and_operation/diagnosis_and_testing/general_procedures/in-vehicle_repair/gearshift_control_shaft_seal/

I cleaned the area behind the plastic cover out with brake cleaner last time I checked the oil level. It was still completely dry this time. 

The oil seems to be leaking from the bellhousing to gearbox joint.

I was typing on a phone when I posted the last reply.

The bottom of the gearbox always has a coating of oil, but it isn't pouring out.

I asked them to check the oil level while the car was on the lift at my last MOT in February this year.

I saw with my own eyes that the level was ok then.

I also checked it myself when I bought the car in Summer 2021. It was a bit over-filled then as quite a bit poured out.

I have an invoice that the clutch was changed in Feb 2019, so I assume that the box would have been refilled with new oil then.

If I have the car long enough that it needs another clutch, I will have the seal done while the box is out.