Re: Advice on oil type sought
Definitely use a C rated oil. You should never use S oil in a diesel except in an emergency and it should be changed ASAP - the additive packages are very different.
Years ago most oils had dual ratings (SF/CD) and could be used in either but the formulations have changed dramatically since then and I know of no oil with dual ratings anymore.
I, myself, personally intend to continue being outspoken and opinionated, intolerant of all fanatics, fools and ignoramuses, deeply suspicious of all those who have "found the answer" and on my bad days, downright rude.