Supposedly, the SM rated oils have other, non VOA-detectable chem-adds to make up for reduced zinc, etc. The newish Rotella T HD 10W-30 is rated for SM, and SL, and SJ, in addition to CJ-4, CI-4 Plus, CH-4, CG-4, & CF-4.
The synthetic 5W-40 is reportedly coming out -sometime- in 2007 in the...