Tried a M1 filter for the first time with the same oil , OCI and conditions on my car and was shocked at how good the oil looked - the only difference was a M1 filter this time versus a cheaper name brand (NAPA) filter that I previously used. I have no regrets with NAPA filters and only tried the M1 filter because it was on sale at AAP . I'll gladly look for M1 filters again and see if my results equal what I observed this OCI .