The applicable manufacturer's specification for lubrication of the vintage Unimog gearboxes is
MB 235.1 and several brands are listed there.
Before we worry about the availability of the listed lubricants in the USA let's look on the German Unimog forums what oils have been recently used and evaluated for their shift behavior:
(The list below was taken from
here and translated. Last update: March 2017)
Type/// mm/s² 40°C /// mm/s² 100°C /// rough shifts when
FUCHS titan gear mp 80 /// 92 /// 10 /// warm (too thin, when warm)
Cartechnic GL4 SAE 80W /// 90 /// 10,5 /// warm (too thin, when warm)
RAVENOL GL4 MZG SAE 80 /// 90,9 /// 10,7 /// warm (too thin, when warm)
LiquiMoly GL4 SAE 80W /// 95,2 /// 11 /// warm (too thin, when warm)
bp Energear EP 80W-90 /// 133 /// 13,8 /// warm (too thin, when warm)
Cartechnic GL4 SAE 80W-90 /// 153 /// 15,3 /// shift mostly well
Rektol Gear 300 SAE 80W-90 /// 140 /// 16 /// shifts very well according to user "martin-w"
RAVENOL GL4 TSG SAE 75W-90 /// 76,3 /// 14,2 /// optimum shift behavior according to user "OPTIMOG" and "KLAUSi". Does not attack yellow metals at 100°C.
Both RAVENOL oils are available in the USA directly from ravenolamerica.com or - in case of the supposedly best performer GL4 TSG - from
Amazon.
I am probably going to give the RAVENOL GL4 TSG oil a try. RAVENOL GL4 MZG SAE80 is listed in MB 532.1 but did not get much user praise. In fairness, MB did most likely not anticipate that their customers would run Unimogs for hours on the Autobahn.
After reading a lot of articles regarding EP additives, GL-4 vs GL-5 specifications, and several TDS/MSDS, I would also be comfortable using
Sta-lube CRC 85W90 (NAPA Part#: SL24239)
Redline MTL 75W80, MT-85 75W85, or MT-90 75W90
I am confident that these are safe for the yellow metal in our gearboxes; what remains is the question about the best viscosity.
Does anyone have any real life experience with the listed Sta-Lube or Redline oils?