The 6.5 Detroit Diesel is one of the most debated diesel engines of the 1990s. In this video, I break down why I rank it near the bottom of my list of HD diesel engines — not because it was inherently terrible, but because of the context of its time. When you compare it to what Dodge and Ford were offering — the 5.9 Cummins and the 7.3 Powerstroke — the shortcomings of the GM 6.5 become hard to ignore. Cooling issues, electronic pump problems, durability concerns, and overall performance left it