My hope, and seems to have worked, was that the aircraft hydraulic oil swelled and softened the seals, and I changed it out before the seals got too big, too soft, or simply dissolved. The 0W-20 synthetic is a seal-swell neutral fluid and of higher viscosity than the brake fluid. I wanted something that wouldn't leak easily.
I haven't looked this up, but the oil probably wouldn't as good at low temperatures (although so far, so good). My guess was that high temperature range would be as good, anti-oxidancy would be as good, water tolerance is probably worse (would separate rather than absorb it). The lucky guess was that the seals tolerate oil; for instance I have seen several type brake dust seal rubbers swell when put in contact with engine oil.
The real benefit came from the AHO 15, a high altitude capable fluid. It must be highly aromatic to cause swelling and probably isn't too common. If you feel you have nothing to lose, try an automatic transmission fluid or power steering fluid with "seal conditioners" or for "older cars." Those suggestions would contain some seal swell additive and be thicker. Together that should reduce leakage and maybe cure a slow leak. Try it for a few weeks, then switch to the synthetic oil?
Usually I try to give out pretty solid, goof-proof advice. I think the above could help, I think it shouldn't be worse, and even if it is worse, it isn't a catastrophic problem, and shouldn't be a safety issue. It isn't a recommended cure-all.
Does anyone have any experience or thoughts on the root cause or mode of failure for this component? My mileage is 6400 and I am the 2nd owner, (Purchased 1yr ago at 4400 miles) should I be preparing for a transmission or clutch failure in the near future? 
Thx
