Lucas Hub Oil WARNING

[Solo So Long]

I just got off the phone with a very helpful guy at the Lucas HQ. I called to ask about using Lucas Hub Oil in our final drives, in place of 80W hypoid oil, and we had an interesting conversation.

He told me that the viscosity is "off the chart," estimated up around 250W. Lucas Hub Oil is intended for use in (wait for it) HUBS of trucks and trailers, to both lubricate roller bearings and keep seals from leaking. The next step up in hub bearing lubrication is pumping in grease.

In other words, it's more of a "goo" (my word) than an oil, as far as hypoid gear differentials and final drives are concerned.

He said that NO MORE THAN TEN PERCENT (10%) Hub Oil can be useful if mixed with regular 80 or 80-90W hypoid oil, to prevent or cure leaking seals, but a higher percentage is a bad idea.

Consider how the oil in your final drive works. The gears ride in a bath of oil, and as the ring gear turns, it flings that oil against the inside of the drive case. This provides a bit of aeration and cooling, as it drips and glides back into the bath to be picked up again. The problem with oil that is too thick is that it is slower to flow and fill the bath. This can lead to voids at the "bottom" of the gear grooves, where whatever oil might actually get there will be thinner than needed.

Hypoid oil doesn't only lubricate the bearings, it cushions the gears as they mesh together, and helps keep the temperatures even and in the proper range. Without the aeration and re-pooling of the oil, this cushioning is reduced. This leads to increased wear of gears, sometimes to the point of fracturing and burning. There isn't a lot of gear surface in a motorcycle final drive, so it is more sensitive to these things than the larger gears in cars or trucks.

So, if seal leaking is a concern, you can get the benefits of the compounds in Lucas Hub Oil with just a little bit, but you want to make sure you're using the right hypoid oil to do the actual work.