I`m cleaning my 04 Rubicon I`m about to clean to stock air filter and in the manual it says to put Pro Honda Foam Filter Oil on it. What does this oil do for the filter and does it matter if I use that exact type?

 

If you dont use filter oil on the filter dirt/dust may be able to get through the filter. You may notice how the oil clings to the outside of the filter? This is due to the oil. The oil also conditions the filter and keeps it from drying out. You do not have to use the Honda brand though. I use the UNI filter oil for mine.

 

Light oils (like motor oil) will tend to dry up after long periods. All the filter specific oils are actually quite thick. My personal preference is Maxima FAB1 spray.