Lubricating Skate Bearings
Proper lubrication of skate bearings (like any bearing) is the key to long lasting, fast bearings. Many skate bearings are supplied with totally inadiquate lubrication for even a day of skating, let alone the expected life of the bearing. Cleaning and lubricating the bearing before use will help ensure maximum performance.
Objective
The goal in lubricating a skate bearing is to surround the ball with a robust film of grease or oil to provide the contact at the races enough support to glide.
A sealed and greased skate bearing is preferred to one that is oiled due to the fact that skateboarders simply do not clean and re-lube at intervals even close to necessary for oil use. Meticulous racers should run an oiled bearing, but only if they clean and re-lube throughout the day. A greased bearing is basically maintenance free, but can be cleaned and re-lubed if need be. See SKF's site for cleaning details. The bearing cartridge is not to be packed full of grease, only enough to coat the actual balls (20% of open space). To much grease causes unnecessary friction.
NTN has an excellent article on bearing lubrication HERE and another article on care and failure analysis [HERE.
Greases
SKF Grease LGLT 2, polyalphaolefin (PAO) synthetic base oils grease with a lithium soap thickener (NLGI Grade 1.5) is considered the standard bearing grease for general skate use. This is some expensive stuff. Maintenance Products Direct caries it and it sells for $80 per 1.0 kg.
Oils
If oiling bearings for max speed, exactly 2 drops of an ISO 13 oil should be applied. Basically you need a grease rated at MIL-G-23827. To understand some more details regarding grease specifications read THIS.
Lubrication tools
About the best way to get grease or oil into a skate bearing is by using a syringe. I found some cheap suppliers online. Microtools has a good selection of syringes, at good prices, with a variety of needles to choose from (15 guage works well).
Products to avoid
WD-40 is one of the worst products to ever use for true lubrication. WD-40 is extremly similar to kerosene. Like kerosene, it does have some very weak lubricating properties but is mainly useful as a cleaning agent.
