You're probably thinking of my post suggesting you can wash out salt after a ride.
We don't get ice on the roads here in Phoenix, so we don't have salt, but we have all sorts of dirt, sand, construction debris, nails, metal and plastic from car crashes, etc., and none of it has gotten into my air-cooled 9C.
Back to the topic of oil-cooling...I just started testing this today with my 36V-Fusin-@48V, which has had problems at low speeds and medium loads where it gets so hot I can't touch it, and the halls stop responding. This is a geared hub, so the heatsoak problem is much worse than a DD. I'm using regular ATF F-type, cuz that's what I had lying around.
http://www.endless-sphere.com/forums/viewtopic.php?f=2&t=15570&p=576368#p576368
So far, the only real test results I have are:
--the hub still works
--the ATF is splashing around inside pretty good, then running down the wiring and stuff into the axle wiring hole, and out the end, despite attempting to seal it with rubber cement (which I didn't expect to work, but the only other stuff I had was automotive silicone that had hardened in the tube and was useless for this purpose).
Until I solve that problem, I can't take it on a road test, as it gets on the rim braking surface, and I only *have* that wheel to brake with right now--the rear has no brakes yet.
I have done no real temperature testing, as it has only been off-ground so far. But at the ~200W it uses at full throttle no load as an overvolted-36V@48V(58V, really) motor, it gets warmish on the outer covers in only a minute or two, while still running the test, whereas before this as aircooled only, it would not seem to be warm at all, until long after the test run was over. Only the axle would seem to be warm (sometimes even hot).
So the ATF is doing *something* for the heat transfer; I just don't know how much. It *should* help keep the motor windings and especially the magnets (on teh spinning bell) cooler, by moving the heat in them to the outer cover much faster than with air only. I think it probably is doing that.
Now I need to find a temperature sensor, like an old BBQ one, and install that when I seal up the axle, and retest without the ATF first, and then with it.