i would warn against mixing synthetic and non-synthetic greases.
i have replaced scores of bearings because of their incompatibility .
It literally can form a ball of highly viscous goo that no longer provides lubrication, quite the opposite- it adds drag, & heat in the process.
Lots of plant mechanics mix syn/non syn greases- then call me in after the failures to clean up the messes they create.
IMO,
Mobil 1 is an excellent choice for your spindle bearings.
if you are going to use the mobil 1 it's best to remove bearings, clean them with solvent, repack with the mobil 1 and then reassemble and set running clearance