Is Oil Viscosity a Concern?

If you’re not than maybe you should be!
Film thickness. Simplified equations have been developed to provide approximations of film thickness with a considerable degree of precision. Regardless of how film thickness is calculated, it is a function of viscosity, velocity, and load. As viscosity or velocity increases, the film thickness increases. When these two variables decrease, the film thickness also decreases. Film thickness varies inversely with the load; as the load increases, film thickness decreases. Viscosity, velocity, and operating temperature are also interrelated. If the oil viscosity is increased the operating temperature will increase, and this in turn has a tendency to reduce viscosity. Thus, an increase in viscosity tends to neutralize itself somewhat. Velocity increases also cause temperature increases that subsequently result in viscosity reduction. From EM 1110-2-1424 28 Feb 99.
Worried about viscosity?

Worried about viscosity?

Increased viscosity leads to increased operating temperature which is not good for either your engine or your transmission (or other mechanicals). That’s why it is best to use the viscosity recommended by the original manufacturers. For example for the L-134 engine use 10 weight in the winter and 30 weight during the summer…or using modern oils you might consider using 10w30. For the transmission, transfer case and differentials use 90 weight during the summer and 80 weight during the winter.

You might be interested in Military Maintenance for MB/GPW Jeeps 1941-45 which has a lot of WW2 jeep or period related topics that might be helpful to you in learning all about the jeep.