There are 2 rules that I stick to (pun intended ha ha) with grease.
1: Never buy more grease than you can use in a few months. Grease is nothing more than oil suspended in a thickening agent. If it sits too long the oil starts to run out. If you go to the store and the top of the tube is dusty or the tube has an oily residue then don't buy it. It has gone past it's prime and the oil is starting to separate. If you get a tube of grease that doesn't seem to want to pump correctly then ditch the grease. It's past it's prime. Someone may have wiped the tube off and stuck it back on the shelf.
2: Don't mix types of greases without cleaning all of the old grease out first. Different types of greases don't mix well and if you mix them you will not get maximum protection.
Have you ever wondered why some people have trouble with bearings despite the fact that they may grease on a regular basis? Even with Extreme Pressure grease! READ THIS before you buy any more grease. It will enlighten you and you can purchase the correct grease. http://www.reliabilityweb.com/art04/...ing_grease.htm
BTW, I used NAPA lithium based grease.