LGR, diesel is a straw man, as you note from the Holocaust Controversies link. the primary source evidence points much more strongly to gasoline engines.
It's one of those amusing elements of Holocaust denial that Holocaust deniers insist on eye-witness testimony, except when it comes to something like references to diesel engines, at which point its sufficient for anybody to say "diesel" for them to say 'see, there's no foundation to the gassing myth!"
the fact is that the testimonies regarding diesel engines are primarily offhand references or second hand, while the people who actually worked with the engines testify to their being gasoline engines:
from the link you provided:
Now let's move to Sobibor. Luckily, we have a testimony of the person who had personally installed a gassing engine there. It was SS-Scharfuehrer Erich Fuchs, who testified on April 8, 1963:
We unloaded the motor. It was a heavy Russian benzine engine, at least 200 horsepower. We installed the engine on a concrete foundation and set up the connection between the exhaust and the tube.
If the people who installed/operated the engines were to testify about them being diesels and Berg's technical arguments are true, that would present a problem. But we have already seen Fuchs testifying about a petrol engine. More information comes from German historian Peter Witte:
In this case even three former Gasmeister (“Gasmasters” / Erich Bauer, Erich Fuchs, and Franz Hödl), who must have really have known the facts, since they all killed with the same motor, confirmed in court that it was definitely a petrol motor. Bauer and Fuchs, having been professional motor mechanics, simply quarrelled during the trial about whether it was a Renault motor or a heavy Russian tank motor (probably a tank motor or a tractor motor) having at least 200 PS. They also disputed whether the method of ignition was a starter or an impact magnet, which diesel motors obviously do not have, being self-igniting...
Hödl reported that they once tried a Diesel motor for the the gas chambers, but it did not work!
simply put, there's no good reason to conclude that the engines were diesel and not gasoline, no matter how many people repeat the error.