LOL!!
Nope, no stock options. Just noticeably better performance on every vechicle I've converted, which have mostly been at 200kmi+ (what DO you consider to be too high miles to switch, anyway?) As to the dealers, well, they are giving you the old CYA line... it's safer to tell you to use dino, because they don't want to be sued if you are one of the 0.001% of people who DO have a bizarre failure. I'm still looking for even one example of a Mercedes diesel engine that had a significant problem after switching, at any mileage (I don't consider increased seepage from bad gaskets to be a "significant problem" though.) In general I agree with Stevo 110% (see his post at top of this page).
That said, if you are using any 15W-50 diesel dino oil and are happy with it, by all means please keep using it! I was responding to someone who was actively contemplating a switch and was looking for good/bad experiences. I will say that the OM60x engines with hydraulic lifters can make noise with dino oil that goes away 90% of the time with synthetics. But if you have an older OM61x, that doesn't apply.
Oh - last note. Although you'd think older MB diesels were designed for "thicker" oil, you may be surprised at what was printed in the owner's manual or factory engine/maintenance manual for those years. Take a look. A better statement is that the newest MB's specify thinner oil, I believe M-1 0W-40 is recommended. I don't like this as I think it's too thin. So I stick with the "thicker" stuff, which - IMO- is no problem for the "old" cars. At least
my owner's manual say I'm using the right weights...
Kind regards,