That M1 15W50 product has been dumbed down over the past few years. It used to carry some other desirable OE ratings but they no longer show.

FWIW, W*mart carries some excellent API diesel-rated oils incuding:

• M1 TDT 5W40
• Shell Rotella T6 5W40
• Chevron Delo 5W40*

All these are great all-season/all-climate oils and reasonably priced. There may also be a Castrol 5W40 product, too. And don't overlook the M1 0W40 which carries the MBz OE certification.

*new, and I'm not certain how widespread the availability is yet.