This can be an important consideration. The refractive index matching and background fluorescence levels of the oil are important, viscosity is another feature, some oil formulations are thinner and spread around more, which is particularly an issue with timelapse - as is drying. Some oils will start to dry out and become very tacky, like dried honey, after several hours. If you are using an oil that drys be very careful as it is difficult to clean the objective and anything else that the oil gets onto (not that that ever happens). There are excellent objectives that are glycerol, silicone, or even can use multiple immersion liquids - I’ve heard silicone is excellent for long working distance, high NA timelapse as the silicone travels with the objective better and doesn’t spread out as much. There are some nice resources out there that have tables of oils and ‘types’, such as Nikon type B, N, F, etc., you should check them out!
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