The thing coming along with the Selective catalyst reduction systems are newer engine oils again, not only are the fuels and emissions systems getting cleaner but they are mandating the engine oils follow just in case an engine were to ..............OMG.....use some oil!!!
There was a huge issue raised in the diesel world with the introduction of API CJ4, just wait a year or two and see what is coming down the pipes in this regard now, this was a big topic that went hand in hand with the talk of the SCR systems discussions.