Replacing depth gauge oil (Dacor)

[tuatua]

I just tried to fix the needle on my depth gauge which was stuck at ten meters this is what I write on my other post......

yes i found something it but it looks like theres oil everywhere theres also a screw there I loosened the screw to my surprise the needle went back to zero I had a look in the screw hole and saw some sand/mud and banged it out.
i took the screw out and it looks like there was oil in the back there that escaped when I opened it does it need to be filled again? i tightened screw back up can I put the rubber diaphragm thingy back on does it take any special oil so I can fill it up myself?

(the rubber diaphragm looks as though it protects the oil from escaping then over the rubber is a metal plate that I removed which also had the writing on it:warning do not press this surface or insert foreign objects through holes) The screw also has hole straight through it for the oil to travel through to the gauge maybe?

Any thoughts on what type of oil to use I saw someone suggest mineral oil but how much should I put in?

 

[tuatua]

This is what the gauges look like trying to replace oil on the back of the right one

http://www.trademe.co.nz/Sports/SCUBA-snorkelling/Full-dive-sets/photos/a-273040401/p-120844410.htm

 

[theduckguru]

If you have a good marine store nearby, fill it with compass oil or a good instrument oil.

Yes, its mineral oil, but likely less viscosity than what you'll buy at WalMart.