I guess with it being an average of 25-30 degs. during the day, and the rush of wind hitting the lower oil pan, the oil is already kept cool. Well at least I hope that's the situation. I don't recall if my ' 80 SD's oil cooler gets warm or not in this kind of weather. I know that even with all that highway speed in the TD, at idle the oil pressure kept up at 2 bar.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member