 They are for conventional oils. With the frequency of my oil changes, I do not see the need for synthetic filters and feel they should work fine. I wonder what your opinion is. Bill, I agree 100%. I don't see the value or the point of synthetic filters, not unless we're going super long distance. I think it's more important to use a good quality oil, obviously, that meets manufacturer spec and change that on a regular basis. I think a good filter that's meeting manufacturer spec...