Packard Motor Car Company once billed itself as "Master Motor Builders"...in addition to their excellent auto engines, they also built the WWI Liberty aero engine (many found their way into race cars, speedboats, and other uses); the WWII "Merlin" Rolls-Royce aero engine (in fact, Packard simplified the design, actually built more Merlins than RR). They had a huge program for marine engines, and PT boats were driven by THREE enormous 12 cylinder Packard marine engines...Packard engines were still working in several minesweepers and other craft as recently as 10 years ago.

BUT Packard also had a diesel aircraft engine as early as the '30s. No details available here, but the plane housing it seems to have been a heavy biplane, which might have the extra "lift" needed to get such a heavy plant into the air. Also possible that Packard diesels found their way into US airships during the period.

Just an interesting side note...MB and Packard shared a lot of common factors in their products and the way they approached business.