I feel the BW4493/94 needs frequent oil changes…regardless of the fluid. When I say frequent, I mean every 10k-15k. It seems very prone to wear and the fluid fills up with metal particulates very quickly (compared to other t-cases). Chain stretch, case rub-thru, loose snubbers, plastic forks, etc. all contribute to dirty fluid.
Borg-Warner cases use an internal oil pump. On the end of the pickup tube, it has a fine screen to prevent shavings & dust from entering the pump. This screen is prone to clogging, and over time this will slowly decrease the effectiveness of the pump. Eventually the pump becomes useless and lubrication is done solely by slinging (like most traditional t-cases). Obviously frequent oil changes will extend the life of the screen and pump. Nobody seems to talk about this, choosing to debate the fluid type itself…rather than the clogging of the screen. If your t-case has been neglected, and you suspect there is a 100k miles on the fluid…the screen will be clogged, and it should be replaced.
https://images.app.goo.gl/q2hrfpjKfcfeWghNA
The BW4493/94 also has an internal magnet to catch loose particulate. However that only works with steel. Most of the loose particles in the fluid are non-ferrous (magnesium, aluminum, or plastic). So the magnet’s effectiveness is certainly questionable. Next time you change your fluid, drain it into a clean pan and toss a magnet into it…you’ll see what I mean. The fluid is often filled with shiny metal dust, and it does not stick to a magnet.
Unfortunately the case must be opened to clean/replace the screen and magnet. I have cracked open several H3 t-cases only to find the screens completely collapsed (sucked flat) and choked with metal dust.