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No, on the highway Cummins and Cat are the champs.
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Indeed. There has been a big push towards four-stroke diesels thanks to “emissions controls” to alleviate so-called “global warming”, thermodynamics of more complex engines and the cost thereof be damned.
I’ve noticed that some Peterbilt trucks are using their own PACCAR (Pacific Car and Foundry) diesels in addition to Cummins.