After 3 solid years of refurbishment I'm starting to blat about in my '87 BDR engined Caterham. The car is running very well and I couldn't be more pleased given the work it's taken to get the car back into shape. I'm currently running Castrol GTX 20-50 in the car and all seems well, oil pressure is nominal and the motor hasn't blown up yet. However, BDRs are not common where I live and finding good information about them is difficult for me. Does the Castrol 20-50 seem like the right way to go? The car is road only (no track days) and is equipped with a wet sump. I know questions about engine oil are apt to bring out a diversity of opinions and I apologize in advance but I really am curious as my usual sources of information are of little use in this particular case.