Grease in an AR is a hard no, it’s associated with stoppages even in hot environments. I tested some personally in a hot/humid env’t and had a lot of FTF. Went back to oil and no problems.
I’ve done a bunch of high round count days with
Slip2000 EWL. I use the heavier stuff, “30” I think. I’ve been using it for years. It does a good job of staying put, lubricates well, and doesn’t smell bad like motor oil. I haven’t tried everything, there might be better stuff out there, but the EWL has exceeded my expecations.