Thanks Easter - I'd read elsewhere about the different colo(u)rs and numerous 'formulations' and would suspect at this vintage it might be OAT, so was hoping the LR guy would have known. One school of thought is it's not just the alumin(i)um engine, but the type of solder used in the radiator (assuming mine isn't ally as well - ?). Also, if it is OAT, and I follow Dave's suggestion and revert to 'conventional' I will need to flush thoroughly - anyone know if these engines are subject to airlocks when draining/filling?
