I have ran Castroil and I thought it was very good
oil. I put over 4000 miles on my race engine before I tore my engine down and there was NOT a lot of gunk inside. I also run 110 Octane leaded fuel when I am on the track so there should have been a lot more junk inside my engine but there was NOT. I do change my
oil before an event and after the event if I have driven very many street miles.
I will either run Castroil or Valvoline VR1 with a modifier, because I run a flat tappet cam and solid lifters. Never had a problem of any kind related to
oil break down.
Clois Harlan