I serviced my wheel bearings for my first time (150 hrs) on my 7 and had lubricated the felts with Mobil SHC-100 as instructed. We know that grease is simply oil mixed with soap and the surface of the contact was blackened. [corrected 4.6.21 by rocketbob - some are thickened with clay] Some have noted to lube the felt with oil.
After cleaning the felts in mineral spirits via an HF ultrasonic device. I applied some 15-W50 Aeroshell to one and Castrol Syntec 10-W40 to the other. Some have noted the availability of the lip seals an they look attractive, but since the inner seal contact sleeves were spinning I decided not to add friction to that ring and make it slip more.
Not desiring to have the oil sling out inside the wheel pant and brake disc etc and gather all that dust and crud,I pondered much oil it should hold?
A test was undertaken. The slinger below was operated at equivalent of 100 mph (2500ish RPM). Too high for landing but it is an accelerated test. The felts were loaded with 1 cc of oil.
Short version - the oil came out as expected and plotting the weight loss of the oiled felt showed that it was beginning to flatten the curve at 2 min. So, a 5 min test was run for the second seal also loaded with 1 cc. The felts were loaded then heated for a few min to ensure full wicking.
The slinger was made from a short section of 2" PVC coupling, carpet tape, the canopy cut off arbor and (yes) some aviation scrap. Epoxy is recommended for the PVC/AL bond although carpet tape worked for 15 min.
Caution - when slinging - put the device down inside a container, as it slings a fine mist of oil you won't see until it is too late. It will also serve as an explosion barrier.
I will return after some experience is gained to see how much oil will contaminate the wheel in real life testing. Maybe the rubber seal is the clean way to go as it seals on the OD if nothing else.