I'm currently running Mobil 1 AFE 0w30 on a 10,000m OCI in my 200,000+ miles '94 Explorer, and the oil has found many small leaks (not enough to ever have to add any makeup oil). I want to change to a HM oil next time. Any reason to think M1 5w30 HM @ 10,000m OCI would work any less at stopping my leaks than say, Maxlife 5w30 @ 5000m OCI? I want to choose the one with the best seal-swelling additives, whether it's conventional or syn doesn't matter.