Skippy,

Dad insisted on an overhaul, even though there was nothing found to indicate one was needed. Our summer temps are above 100°F and in the winter, it may go as low as +28°F, but usually, it doesn't get much below freezing here in the valley.

Again, I suggest you use a thermostat. However, I think 194,000 miles is proof sufficient that you will not destroy your engine by driving it at 60°C to 70°C as some would postulate herein.

When I bought my 1978 300SD from the original owners, it had a 60°C thermostat in it and when I went to the parts counter and asked for a thermostat, they gave me a 60°C, so that is what I used for the 87,000 miles that I put on the car before I rebuilt the drivetrain at 311,000 original miles...Robert