The spring tension over the check valve is barely enough to keep oil from draining back in the sump. Contrary to Various other engines that run them at better RPMs the 4A-GELU squirter is in regular operation, aiding in cooling and lubrication. I have study that the 5500 rpm limit https://spenceravioa.ltfblog.com/26375846/the-4age-20v-diaries