What’s that you say? That’s the same thing I said. As best I understand, most cars have sealed bearings on the front axle (free wheeling) wheel spindles.
The Freightliner chassis on this motor home however has refillable oil reservoirs on the front axle spindles. 
After removing the chrome center cap, the reservoir is exposed and there is a rubber plug. They say that eventually the rubber plug gets dried out or the seal behind the flange starts to leak. You can see the oil streaks/drips in the picture to the left.
Fortunately, we were only about 10 miles from the Premier Truck Group of Tulsa, a Freightliner dealer owned by Roger Penske. They came right out to look at it, got us into a service bay in short order while Kathy and I had breakfast at Waffle House and then we got the toad washed to kill a little more time.
They checked it out, replaced the leaking hub gasket, refilled with 85W140 oil, cleaned up the wheel and had us back on the road in about 3 hours.
Thanks much to Matt at the service desk and the rest of the crew at Premier Truck Group for their great service.
