Though automakers like Stellantis, Mazda, BMW, and Mercedes-Benz are keeping a few straight-six engines alive in 2025, there are currently just two straight-six diesel powerplants left on the market. Both of them are American, and both are in pickup trucks. Below, we look back at the history of each, as well as their modern-day technical feats and specs, along with the vehicles they power and what you should expect to pay for one today.
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