Diff oil level

[guye]

Newbie question. I need to be sure the oil level in my diff is OK.

I know the diff oil is meant to be filled to the bottom of the fill plug (or max 6mm lower), however it is practically impossible to see in!

I've made a small dipping wire but I think it gets 'oiled' when I touch the entrance to the hole, so am not confident this is accurate.

Best effort was to shine a torch, and then spin the wheel so the gears upset the oil to create a ripple, but I'm still not confident.

I filled it from empty with 1.15 litres (1 litre oil and 0.15 LSD additive). Its a 3.45 LSD ZF diff.

I could buy another bottle, of oil and fill it till it drains, but that seems pretty primitive and wastefuly (doubt I'll use the rest of the bottle for years!).

So I used my Aldi special inspection camera and took a crappy picture while I was turing te gears again. Hopefully some of you will recognise the gear and the oil level and tell me it is full!

The arc at the bottom is the lip of the fill hole.