We have recently had a lot of work done on our OC-12 including new brake drums, bands, actuator rod sealsl plus replaced axle outer bearings and sealsl The iunit also has a small circulating pump that is powered by the hydraulic system. I have read several posts that seem to give conflicting information about what fluid should be used in the actual OC-12 differential steering housing (depending on the authors take on whether or not it was tied into the main hydraulic system). My manual says Conoco DN-600 fluid should be used and that fluid is also used in the outboard reduction housings. I'm finding a mish mash of information about what the correct replacement for Conoco DN-600 fluid is isince the 600 is no longer available. Any one have an answer?