FORD 2012 F-550 v.3 - Manual (Page 347)

On all two-piece flat wheel nuts,
apply one drop of motor oil between
the flat washer and the nut.
WARNING: When a wheel is installed, always remove any
corrosion, dirt or foreign materials present on the mounting
surfaces of the wheel or the surface of the wheel hub, brake drum or
brake disc that contacts the wheel. Ensure that any fasteners that
attach the rotor to the hub are secured so they do not interfere with
the mounting surfaces of the wheel. Installing wheels without correct
metal-to-metal contact at the wheel mounting surfaces can cause the
wheel nuts to loosen and the wheel to come off while the vehicle is in
motion, resulting in loss of control.
Inspect the wheel pilot hole (1) and
mounting surface prior to
installation. Remove any visible
corrosion or loose particles.
Roadside Emergencies
347
2012 F-250/350/450/550 (f23)
Owners Guide, 3rd Printing
USA (fus)