Steve.
The oil Brayco Micronic HT 200 is actually the same as Castrol Brayco Micronic 864 HT200 (Synthetic Hydrocarbon Based Subsea Control Fluid).
'Castrol Brayco Micronic SV/200 has similar physical characteristics to the Castrol Brayco Micronic 864HT/200 and 865 grades. Extensive physical, chemical and performance testing has demonstrated that Castrol Brayco Micronic SV/200 is fully compatible and miscible in all proportions with the Castrol Brayco Micronic 864HT/200, 865 grades as well as the low viscosity syntetic Castrol Brayco Micronic LV/200'
..From castrolsubsea.com
I recommend their web site for more excellent information on ther special fluids. Here is an direct link:
http://www.castrolsubsea.com/bcweb/subseadownloads.nsf/frmWelcome?OpenForm