Why diesels are most efficient around 1,800 rpm

Sounds like this guy likes to tow in 5th for many of the same reasons as Shiner but he does indicate he gets slightly better fuel economy in 6th. He might have slightly bigger tires? Seems like splitting hairs to me. I’m certainly going to go for the quieter cab with the lower rpm if I can save a few pennies at the pump. If the transmission needs to be babied to handle towing light why not just buy a Ford?

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