Death by diesel exhaust was proven in this case, which presented a blood test showing a 67% concentration of carboxyhemoglobin in the victim's blood. It also admitted "testing by Bredemeyer and Miller on a Freightliner truck with a Detroit Diesel engine, Series 60" which showed "that the truck could produce enough carbon monoxide to kill a person." Furthermore, Berg's site has this study, which states that "The available literature concerning the CO content of diesel fuel recognizes its potential lethality under certain circumstances." Berg himself agrees that "carbon monoxide levels in Diesel exhaust can kill under heavy engine loads (Buchanan is mistaken in this regard)", although he thinks that it is absolutely absurd to use diesel exhaust for mass murder.
Consequently, although we still regard the diesel issue to be irrelevant, we can categorically state that diesel exhaust can kill humans, contrary to the claims made by Pat Buchanan, Arnulf Neumaier and your average CODOH chimp [1, 2, 3, 4, 5, 6, 7]. This does not prove that diesel kills as efficiently as gasoline, nor does it prove the timescale of killing, but it removes the simplistic canard often seen on Internet forums that diesel cannot kill at all. This accidental death by diesel exhaust also makes it harder to claim that diesels could not have been adapted for mass gassings (although we don't claim they were).