What is this type of leak called?
Can I just pump in some gear oil into the square bit drain plug ?
Is there a stop leak product that works ?
How much does this cost to repair correctly?

 

1. Front differential pinion seal leak
2. Yes. (it is a fill plug - not a drain plug)
3. Perhaps. If it is an old hard seal, but undamaged, a stop leak product for seals may or may not help (they work by causing the seal to soften and swell up slightly)
4. $375.14

 

$ 20-30 dollars for the seal and gear oil, the good news is you can change the seal with the front wheels on the ground in case you still haven't figured out how to jack it up.

 

No thanks. I only work on my German cars now
I'll let a pro fix it the leak next time it's in the shop.

 

Very easy to replace, just did mine last season. Paying a pro is going to cost you.

Probably cost me $20 to fix it myself.