The reduction in ZDDP is for nearly all diesel rated oils (Rotella T4 is one) came about with the introduction of the API CK-4 rating. I have oil analyses that indicate that happened around 2018.
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.
