Greasing Type for "Sealed" Joints

If I was to use the injector needle to lube my ball joints as a "preventive measure "(they are fine now). Is that a smart idea and what type of grease would be most compatible with the grease that is already factory sealed inside. Like I said, they are fine now, but I am hoping to extend their life before I get a problem. Pros and Cons readily accepted.

I think that I ended up using Mobil 1 synthetic grease. There are a lot of good quality grease brands out there. Valvoline also makes a synthetic.
Be careful to avoid over-doing it. The grease comes out of that little needle faster than you will expect it to. If the seals are not collapsed.....just a little bit will do.....stop when you see any movement of the seal. If they are collapsed....stop when they start to fill out.

I poked the needle righ into the side of the seal.

The reason I am asking is that I purchased one of the small grease guns that comes with a cartridge of grease that is supposedly good for ball joints, etc. The grease is dark black (contains moly). Would this be OK for greasing my ball joints? I dont want any compatability problem with the grease currently inside.

The grease that came with the gun is Pennzoil Multi-Purpose 302 EP grease with moly.

This is one of the worst ideas anybody ever came up with, that piercing the boot is a way to grease the joints. This will actually reduce the servicable life of any joints greased like this. Putting grease in the boot WILL NOT HELP lubricate the joint. Take a look at the aftermarket joints the grease fitting is on the opposite side of the boot, they are made like this for a reason this forces the grease through the joint and forces the old grease out of the joint. Putting a hole in the boot just gives water and small dirt particles a way in.

Before I owned a Ford Windstar I would agree, and used to laugh at the idea of greasing a sealed joint. But in the case of the Ford Windstar OEM tie rod ends, the grease needle has worked well. I think the case to use it is when the component is making noise (ie dry), with no other steering issues. Based on most posts you see here and the old Cartrackers forum, you are lucky to get 50k out of the original OEM "Sealed for life" tie rod ends. No one is claiming that this replaces old grease with new, it merely adds some new grease to a dry component.

In my case the tie rod ends starting making noise at only 45k with no other driving issues. At that point they will not last long before having steering issues. So the choice is replace the tie rod ends at a ridiculously low mileage, or just add some grease via a needle to an otherwise dead component. I added grease, and with a needle that small the hole seals up on its own. Well that was 10k ago, no noise or issues since.

I think if we went through this forum and the old Cartrackers forum you'd find dozens of similar experiences with the Ford Windstar OEM tie rod ends.

Since getting the needle have I used it on my Nissan? Heck no, their sealed for life components actually last the life of the vehicle. But in Ford's case the tie rod ends fail at very low mileage.