When doing a filter change on Cat 3516's, does anyone else rotate the Aux. filter out and place that filter into the main filter housing along with two new ones, and then put a new filter into the Aux filter housing. I have been on vessels where we did not touch the Aux filters and only replaced the main filters with new. The theory behind this is the Aux filter is sitting in fuel or oil for who knows how long and getting gummed up and will not be as good as a filter that is only been sitting in the housing since the last change of the main filters.
I don't think I have ever been in the situation where we needed to switch over to the Aux. filters so not sure if this even matters.
Thanks for your input.