Originally Posted by
JohnDThompson
How long it takes for the oil to separate from the surfactant depends on how well the grease was emulsified in production. Cheap greases will separate faster than better greases. My experience is that good quality grease like Pennzoil #705 and Campagnolo grease can go years without separating, while bargain auto parts discount store grease can start to separate in a few months.
Perhaps but most people will..and did…give the advice that “grease is grease”. That was also likely the reason that the suggested interval for greasing bearings was about 6 months or twice a year. Soap based greases could, in theory, wash out because the soap is a soap and can be slightly water soluble.
Modern polyurethane greases don’t have that problem because they don’t really separate.
N.B. this separation issue is a reason why many old-school cup-and-cone hubs have an oil port where you can add more oil to replace that which leaked out. The act of riding will re-emulsify the oil with the surfactant and restore the grease.
That’s really, really, really, really old school. I seldom see a hub with the ability to add oil to the hub and I see a lot of what could be considered to be antique wheels.