Ok to run 0 or 5W-50 fully syn. in 86 190E to quiet lifters?
 

Or 0W-50 fully syn? Currently I have 10W-30 Mobil Fully Syn. The purpose would be to further quiet the lifters as they are noisy until engine is hot. My valve cover gasket has been recently replaced and I experience no oil leaks. Thanks

Well, Mobil 1 0w-40 is on Mercedes' list of approved oils. It's not easy to find, at least where I am, but it could be a good bet for you. There are a few other 0 weight oils on the list, which you can see at the link below.

http://www.whnet.com/4x4/oil.html

I would recommend against using a full synthetic oil in a high mileage engine to begin with.

Secondly, have you looked into the replacement of the tappets (lifters) ?

Yes, I can have the lifters replaced. I am curious as to why a fully syn. would be bad for a high miles car though?

my 250SE runs fine on 5W40 fully synthetic. No oil leaks :)
Though a week ago the head cracked. So i'm up for an engine rebuild.

Manya,
I'm not so sure it runs fine, not if the head cracked! Seriously though, not suggesting that the oil caused it. Sorry to hear of your bad luck.

Scott,
I think the lighter viscosity oil may help, but is not really the solution to the problem. My 190E also has a couple of lifters that are intermittently noisy until the engine reaches full operating temperature. I have found that the 15W-50 in the engine at present needs more time before the lifters quieten than the previous 10W-40. Lifters are not that expensive and I have every intention of replacing them. It needs a new valve cover gasket anyway and I am also tempted to do something about the blistered and peeling coating on the valve cover.

Greg