| use Slick 50® Diesel Engine Treatment which is specially formulated for diesel engines (got that off the Slick 50 web site). But that being said I would never use it myself! It is pretty thick what will it do when it passes through the injectors? I would imagine most of it gets "sucked" in the oil filter anyhow.
But hey you never know... I did not even know they still made this stuff! | 
