Bonjour,
In Stuart steam machines world for example, the manufacture has chosen the "dead led" what I call a displacement lubricator:
Microcosm/Okmomodel or JMC in France, for example, have chosen the "flow through" ones :
To my opinion, the first option is not the best one because the RC steam valve is not lubricated.
This is why, on this example, I replaced the original "dead led" one by a "flow through" one :