DURAMAX Diesels
For a quick brief history GM started a quest to enter the diesel market with its own engines in the early 80's with their now infamous 5.7L in their Buicks, Oldsmobiles, Cadillacs and of couse the GMC's. After America discovered the inadaquate attemp at converting a gas engine (350V8) to diesel, the market for the diesel engines fell to the medium and heavy duty trucks only and to Dodge and Ford.
After several years of gas only production GM finally came out with their 6.5L and later their 6.2L diesels. The 6.5L was a 400 block V8 w/4 bolt mains and a case hardened crank and cam assy. which eventually wound up in the Hummer and was delivered to the Military.
The 6.2L though was a TRUE diesel but WAS NOT built by GM! It was built by a company that they were and are a major investor in called I S U Z U....
By the way, Japan and Isuzu have had the lead in clean burning and powerful engines for years, ahead of even the Euopeans until the last couple of years-Note the AUDI R10TDI which won the 24 hours of LeManns again this year.
Since then there has been many changes and as one of the responders has said the motor is now built in America.
Engineering by Japan but MADE IN AMERICA! ! !