Let's try this. The correct API rating for "light duty" diesel service (and ALL automobile and pickup truck diesels are "light duty" diesels) is CF rated oil! That's the CURRENT API standard - not something from the dark ages. Many CF rated oils do NOT meet either the ACEA or the Mercedes 228.x or 229.x standards so should NOT be used in Mercedes diesels, but the ACEA and Mercedes standard for light duty diesels are much different than the standards for BIG diesels. There are CF and higher (CG, CH and even CI) oils that DO meet the Mercedes standards and are thus entirely adequate.

A higher TBN is of NO advantage or benifit if increased acid neutraliztion is not required (and with 5-15kmi oil/filter change intervals and low sulfur fuels increased neutraliztion is USUALLY irrelevant). Increased soot suspension characteristics are not required and may not even be desirable if soot levels are expected to be kept below 2% even if the oil could hold more soot in suspension (as is the case with ercedes light duty diesel engines). Mercedes uses frequent oil changes to keep the soot levels below 2%.

With suitable soot filtering, Mobil 1 can be (and has been) used for 50+kmi in light duty diesel service before the TBN drops to the point where the oil needs to be replaced.

Discussions with the tribologists at Mobil over the last half dozen years have provided me with MOST of my knowledge on the subject. They first pointed out that there is NO advantage to using CG or higher rated oil for light duty diesel service. They agree that their Delvac 1 is "better" oil - having many superior characteristics - but they also point out that those characteristics will not improve the life or performance of a light duty diesel in usual applications in any measurable way - even over hundreds of thousands of miles. One of the engineers had a 123 300TD that he'd bought new and had traveled 225kmi when we talked. It had been "fed" nothing but Mobil 1 since the first oil change and he claimed that the timing chain stretch was less than 2 degrees and that valves seldom required adjustment more often than every 50-60kmi. I ask why he didn't use Delvac 1 and he insisted that it would have changed NOTHING.

Delvac 1 is a more "refined" and complex oil product and a VERY good one, but it is NOT required and offers NO detectable benifit in light duty diesel service. When I get it for the same price as Mobil 1, I use Delvac 1 (I really like the 5W40 viscosity) but when Mobil 1 is 20-30% less expensive, the Mobil 1 is entirely sufficient.

Marshall