I have ' 92 SL2 since new with 120K on it now. It does use some oil but
nothing yet to be concerned about between 4K oil changes. Currently am
using 10w30 as I always have. I have access to good quality bulk oil
in two grades, either 10w40 or 15w40.

It seems in past postings I have read, NOT to use 10w40 in newer modern
engines. I don't have a problem with the 15w40, but could someone
explain the reasoning for the 10w40 issues, if any at all. Everyone's
opinion are appreciated.

Thanks, James