This doesn't pertain to diesels a whole lot but it could be of some importance (Jeep is using Mercedes diesel motor in the Liberty). I haven't done a whole lot of research on it but I am very curious to know and this is my understanding so far.

Ford, Lincoln, Mercury, Volvo, Mazda, Aston Martin, Jaguar, Lotus, (Maserati?) (Saab?)

GMC, Chevrolet, Oldsmobile, Buick, Pontiac, Cadillac, (Isuzu?)

Plymouth, Chrysler, Dodge, Jeep, Eagle, Mercedes (Plymouth and Eagle no longer producing vehicles) all owned by Daimler-Chrysler Corporation

Volkswagen, Audi, Porsche, Lamborghini

Honda, Acura

Nissan, Datsun (Datsun out of biz)

Toyota, Lexus, Scion (I thought Scion was a Toyota model but I was recently at the Toyota dealership and learned that it is a make and they have 3 models so far www.scion.com)

Independent?????

Mitsubishi

Subaru

Saturn

Let me know if I missed any or if you have any discrepancies and which companies are solely independent?