Engine life
Wow! I read so much information in this post that my brain must have "information overload".
I run 15-40 oil in the summer and 5-40 in the winter. Keep the road speed at
about 50 mph and try not to abuse anything.
Perhaps the problem in southeast asia was the heat/humidity? In Vietman's hot
climate and combat conditions, those trucks that broke down might have simply
been pushed too hard and overheated; leading to engine failure??