Occasionally it will be necessary to flush the oil system because of an accumulation of sludge or other foreign material.

I like to keep my jeep clean.  Don’t you?  Here’s some instructions straight out of WW2 that will help you keep clean…the jeep that is.

Drain the oil from the system after warming the engine to normal operating temperature. Be sure to use CAUTION as the oil will be HOT.
Fill the oil pan to half the indicated level with light engine oil.
Start the engine and allow it to warm up thoroughly. This will allow the light oil to clean the system. Watch the oil pressure gage, and stop the engine at the slightest sign of low oil pressure. This may be caused by a clogged strainer.
When the engine is thoroughly warmed, turn off the engine and drain the oil.
Fill to the proper level with the correct engine oil.
If the oil filter has a replaceable filter element, inspect it and replace if necessary.
Caution: These are recommendations from WW2, always consider if this practice is considered safe for you or your equipment for proceeding. If you follow these instructions I would use extreme caution and watch closely the oil pressure gauge. I would also using 10w oil as my “cleaner” and I would fill it till it was at the full mark instead of half. The sump pickup in a jeep may not pickup the oil if it is only half full. I suggest always changing the oil filter when changing the oil. But I wouldn’t change the filter until after the cleaning. Again, exercise caution.

The Complete WW2 Military Jeep Manual contains many more procedures that will help you with your WW2 jeep.  If you don’t own the WW2 jeep manuals–you need them!