Those trucks were BEAT on.
After sitting all weekend you would hook up the air hose to your truck and fill the air tanks for the brakes and suspension.
While that was filling you checked the oil and coolant and trans and hydro oil levels.
Then once the tanks were full you started it and idled out to the loading station (150 ft away)
Then you set your drum to spin as fast as it could and then you locked the throttle wide open, mind you the truck has been running all of 2 min at this point.
Once you were loaded (15 min, depending on the load size) you returned to idle and then backed away from the loading area.
These trucks are ran at the governor for hours on end in 90+ temps with 40,000 lbs of cement inside the drum.
The temp gauge was near or in the red most of the time.
You start the truck in the morning and NEVER shut it off until the end of the day, you shut it down and you were screwed.
After running a load you took your water hose and sprayed the radiator to cool it down and rinse the dirt off of the fins.
The radiator was in the back so the trucks ran hot anyway.
Rotella is great stuff.
If it can stand up to a overheated big bore big cam diesel with a glowing hot turbo working its butt off all day everyday then it is good enough for my Disco.