That's cuz you are burning it all out! Two things - first, the "seal" around the diff mounts are just liquid gaskets - if the bolts back out and the diff starts to move around some, sure, it will leak. Tighten them back up and it may go away. This is the case on my VX. Second, the pinion oil seal... if that is what is leaking (again, such as the case with my VX) the front driveshaft would be removed, the pinion nut removed, the yoke removed, the oil seal removed, the crush collar removed, a new crush collar installed, a new oil seal installed, a new pinion nut installed - everything else would be reused but the preload will have to be set by a pro unless you can find access to the appropriate tool to do it yourself. If it is your oil seal at the pinion, parking on an incline will usually force fluid past the seal - it might not leak otherwise... unless of course when driving.
When you say oil around the pinion seal, is that the engine? Sorry, I'm not that up to speed with all yer technical mech 50cent words. I'm still learning.