I simply want to know when 15w-50 is acceptable for use. It is recommended in the manual for my '90 300CE as an all weather oil, as is 15w-40 and 10w-40, but it seems like it would be awfully thick unless you live in the desert (I live in DC).

The PO provided records with the car indicating oil changes with Amsoil 10w-30, but the owners manual states 30 weight is only recommended for temperatures under 50 degrees. The last oil change I did I just put in Chevron Delo 400 15w-40, because I couldn't find any synthetics locally in that range. Although, I did find Mobile 1 15w-50 at Walmart, so I am considering weather that is a good option. Another option is Amsoil 10w-40, but hasn't it been determined that 10w-40 has too many additives and that a 15w-x is preferred?

I don't mean to start an oil war, I just want to hear opinions on 15w-50.

Thanks,

GregS
'84 300D
'90 300CE