Lubricate the rubber seal. A dry seal would stick when installing the filter. Oil helps it to slide a bit on the mounting surface and compress, thus giving you a better seal.
Unlike the engine oil filter for the Komatsu PC200LC, Shawn didn’t prime the hydraulic oil filters for the Yanmar C50R. Why?
The first reason is that the filters protect different systems.
Many people prime engine oil filters for fear of excessive wear, while others don’t for fear of contaminating the engine system. However, as our Komatsu PC200LC 1000-hour service article discusses, even manufacturers don’t entirely agree on this topic in their equipment manuals.
In this case, the filter is in the return line, no sensitive pieces are in the reservoir tank, and the oil will go through the main filter further down the line.
Install the filter by hand, turning it clockwise. As we encourage and recommend in most articles, don’t install spin-on filters using a filter wrench.