Ant I agree with you on some of the things. The guys around here that dirt track run 40-50 microns in Omni filters. Some of the older guys are running Wix and have no problem with them either. It's all how much is in the pocket.
My only concern is airation of the
oil. Depending on which
oil wieght, sythesic like Mobil1, or
Amsoil, and how bad the track is for dirt in the air for how small you can go with micron range and have a small pressure lose. I run a small fram 3780or 3870 on my car. It's a peanut. So far it's takes the 135 psi for cold starts and seams to have good flow for racing. When I go dry sump, I will go with a 1 1/2
oil filter for this motor. I do stay away from any dual filters that have paper and cloth in them, Like some of the Frams and STP's. I will say that the oil from these filters seamed to stay cleaner longer. I did think there is a pressure drop with them. I have always run HV or HVHP oil pumps with a min of 60 psi at 2,000 rpms on any of my motors. I also have started to add accusumps to all my trucks for peroilers. What are the jet boat racers using down there? Rick L.