From their site: sounds interesting...
One reason the public confuses the Optimizer 6500 engine with that of the earlier GM 6.2L and 6.5L is that although not in anyway formally tied to General Motors, AM General produces the Humvee and Hummer vehicles as a supplier to General Motors. Having produced these vehicles in previous years as well, AM General was using the GM produced 6.2L and 6.5L engines during that time. When General Motors decided to sell the engine rights to the GM 6.5L engine family, AM General quickly moved on securing the overall engine requirements, however decided to make major product design and durability improvements by introducing the Optimizer 6500 in place of the earlier GM 6.5L models. Since most of the public is familiar with the Humvee/ Hummer and the fact that several 100,000 of these vehicles have been produced with the earlier GM 6.2L & 6.5L engines, they automatically assume the current 6.5L engine offering to be the same GM 6.5L.
Another common mis-conception is that the MarineDiesel product line being based on a 6.5L engine design (Optimizer 6500) is therefore comparable to the engine offerings of our competitors. The truth is that MarineDiesel never produced any marine engines based on the GM 6.2L or 6.5L engine. MarineDieselGÇÖs competition cannot make this claim and therefore many of the issues customers relate to the competition are based on products produced and sold using the GM engines.
If someone claims the MarineDiesel is built on a GM engine, a Detroit diesel engine, the same GM engine in thats been in the Hummers for years, that AM General is part of or owned by General Motors, that the MarineDiesel can be compared against competitive 6.5L based products, etc, you can be sure that the source of this information is out of date and not correct.
The AM General Corporation is best known for manufacturing the Hummer, and military Humvee vehicle product lines. The Optimizer 6500 is the same engine currently produced not only for various pleasure and commercial applications, but also for the military Hummer vehicles. To date more than 50,000 of the latest design Optimizer 6500 engines have been produced and sold, yielding some of the industries lowest warranty service claim rates. The base engine is produced by AM GeneralGÇÖs General Engine Products division at their state of the art Franklin Ohio plant, adhering to extremely stringent QS 9000 certification guidelines. Currently, AM General produces the High Mobility Multipurpose Wheeled Vehicle (HMMWV pronounced HUMVEE -«) and the HUMMER-«. In addition, General Engine Products Inc. (GEP), a wholly owned subsidiary of AM General Corporation, produces OEM 6.5litre diesel engines, both naturally aspirated and turbo-charged, used in military, automotive, marine and various other industrial and commercial applications.