87 sdl 5w40 rotella syn now blk smoke

[rsieracki]

Hello all,

on sunday i changed the oil in my 87 300sdl (225k). i purchased car in june 08. had oil changed at my indy as no one in town stocked the filters and i was headed out for a lil road trip in august. Ok so now i get a filter, get some Rotella 5w-40 synthetic and change filter and oil. car ran noticably rough on startup and also did yesterday and today on statup (but getting better maybe this is normal when very cold out)but runs better once warm and also quieter. but when i initially started it up after the new oil change it blew black smoke and black stuff out the tail pipe (had an old gas engine truck that blew black stuff that meant it was running rich). from what i was told the the p.o indy that i bought car from (not my indy but his friend) it had regualr oil changes and didnt require synthetic. did i create a problem by switching to synthetic or is this simply the synthetic cleaning crap out of the engine and some ends up in the tail pipe on startup?

sorry if this has been covered but i have searched around on this forum and others and cant find much info. if it has been covered, just supply me with a link.

thanks
Ron