Drove one through my time at A&M in the 80's. Never gave any trouble, but is what TSW2012 said it was. Remember that automotive diesels of that vintage were really built for economy, and that was marginal. I would leave home for school and always switch tanks around schulenberg, that was 15.5 mpg in a C30 w 4.10s
My dad had an 83 K5 Blazer with the 6.2 diesel. I don't ever remember any issues with the motor but that thing shredded transmissions. I think he was on #3 when he sold it when not a ton of miles.