The "diesel oils" have also been affected recently. The API-spec "CI-4" diesel oil (which has a very high level of ZDDP) has been around for a long time (Shell Rotella, Mobil Delvac, etc.). However, the new EPA Tier II Bin 5 diesel emission requirements that go into effect next year require the use of catalytic converters and particulate traps, which are "poisoned" by the high level of ZDDP in the CI-4 diesel oil, so there's a NEW diesel oil, API spec "CJ-4", with a much-reduced level of ZDDP, intended for use with the new low-sulfur diesel fuels in the 2008 Tier II-regulated diesel engines.
CI-4 diesel oil offers better protection for sliding elements than the new ZDDP-reduced CJ-4 diesel oil; diesel oil used to be diesel oil, but now there are two DIFFERENT diesel oils.
