some more fun times... this makes you question what the lesser of the two evils is.
"This will probably start a shit storm but...Rotella T-6 is an amazing oil. The reason it has not gotten the MS-12991 certification is because Shell has not pursued it and because they don't need it. They have far more business than they need without chasing the VERY limited Eco-Diesel market. Remember it cost MONEY to get API certifications. and it's all about the mighty dollar.
That being said, the most important component of the MS-12991 for these engines is ASH CONTENT, and the ash content of Rotella T-6 is the same as MS-12991. Ash is kryptonite for the DPF. Metallic and semi-metallic ash will not burn off in the regen process, when it will build-up and eventually plug/restrict flow.
Study the ash content of MS-12991 and look at competing oils and you'll be fine.
Another angle to consider is, ash is added for lubricity...better ash content, less friction, less wear. Lower ash, more friction, more wear BUT less particulates in the DPF. With stringent EPA rules/restriction, and to meet these requirements, manufactures are sacrificing engine longevity to meet clean air standards.
As far as Rotella T-6 causing failure of a turbo, I'm calling bullshit. Anyone with technical knowledge of turbo operation will agree...with two spinning wheels suspended by sleeve bearings and proper lubrication (not coking of course), a turbo will last the life of an engine. "