Patman,
driving style/transmission choice must have a bearing on it also.
Watching my parents drive off yesterday, Dad was running quite low revs, and moving off loaded up a hill. Came close to stalling, and you could hear the clacking detonation as he drove through the near stall.
His bearings must have copped an absolute pizzling in that instant.
Went for a walk down the street, and at every hill intersection, on the hot day, you could hear cars knocking through not enough revs to move away smoothly.
Maybe the heavier weights protect a little better under these extreme conditions, I don't know.