20W50 and Valve Sticking

[ChinaClipper]

Any general thoughts, pro or con, on using 20-50 in my 86 190E 2.3, 8 vavle or 86 300E? The Denver summers are kinda warm (not yet!) but we occasonally have cool mornings that would make 20-50 a bit thick. I understand valve sticking, amoung others, is a possibility under these circumstances. Any ideas on the potential benefits of thicker oils in engines with over 140K mi? Thanks....