The folks at Henschen I talked to have no opinion or recommendations on synthetic grease. Dexter recommends Pennzoil Red Synthetic Grease. I have not been able to locate any. Mobile 1 grease is available just about anywhere. Amsoil can be ordered by their 800 number or website. I have ordered the Amsoil grease for when I repack mine. It is recommended that wheel bearings on travel trailers be done once a year or 10,000 miles, which ever comes first.
A friend of mine has a tandem axle forklift trailer. It has Dexter's dura-flex axles on it. He lost an outer bearing on one wheel a couple of weeks ago. I looked at it, and the grease was very dirty looking. He estimated the bearings were done 5 years and 250,000 miles ago! It had zerk fittings on the hub covers. It looked like someone had pumped in too much grease and blew the seal out a while back.
2003 GMC 2500HD 4X4 D/A Ext. Cab
Propane Powered Honda EU2000i
Lots of Hot Sauce!
Air # 283