The Shell Rotella T multi-grade 15W-40 oil appears to be non-synthetic (I am noting this because this thread started out with a question about the use of synthetic oils in 216 engines).
tclederman is correct. Is the Shell Rotella T SB (Synthetic Blend) getting confused with the Rotella T Multi-Grade or are some of you using one and others another? Not trying to highjack the thread BTW.
Don