hi,

my 1983 MB 300D runs quite well, but can get hot 100C or a little above) when running on hot days with AC. Usual operating temp is more like 83-85. Ive heard that synth oil has better cooling behavior in autos, so the engines and cooling system requirements can be lowered. Is this true? Since I have an oil cooler on my car, if I used synth, would I notice much of a diffeence?
Thanks

JMH

Stay away from synthetics on this car (Please don't let this start a dino versus syn debate - there are already enough of them). Go with a good quality diesel rated oil like Delo 400.
Check your coolant to water ratio. I have found 40% coolant, 60% water works pretty well along with a little water wetter. Make sure all the cooling components are working good. When was the last time the cooling system was flushed? I would be surprised if your oil cooler thermostat ever opens sending oil through that cooler.

__________________
Jim