DON’T USE GREASE! It will make a mess every time you put the key in. Plus grease + lock mechanisms = bad. It can cause a pin to hang up from suction and you are done. The lock won’t turn. Remember the pins go up AND down as you insert the lock.

I buy a THIN teflon based lubricant from my locksmith called Tri-flo. This is what the ‘professionals’ use.