Also MB will not give their approval unless provided with the formulation details of the oil - something not all oil manufacturers are prepared to do (confidentially agreements mean nothing in this age of the internet) which is why the only oil on the market to meet API CJ doesn't have MB approval.
Interesting. I used to work for MoD in their Mechanical Testing of Lubricants Laboratory testing oils.
The American Petroleum Institute publishes its specifications that oils have to meet. They also use industry standard test engines and standard test routines.
So an oil company will blend a candidate oil to just pass the spec they are trying to achieve and test it in their own facilities. When they have an oil that passes the API spec they then submit a sample for certification to the API. If the oil passes they test the oil is awarded a certificate. Then the oil company will brand the oil and can put the API spec on the bottle.
As for chemical formula not being published. Well the chemists I used to work with would happily provide a chemical formula to all oils we used to test. I dont know how long it took but it was only a couple of days max before we had the chemical results.
The mechanical engine tests used to take us a minimum of 5 weeks!!!! As we used to run the engine on a known reference oil, then the candidate, then ref, then candidate, then ref. Each test was carried out on the same engine block and head but with new bearings, new piston and rings, new piston liner etc. for each test.
I would guess MB produce a specification that an oil has to meet to be given the MB code. I would guess that the oil companies provide a candidate to MB and MB get an independent test house to carry out the tests. If the oil passes it can use the MB code number. I guess this costs the oil companies a fair few quid!
Lastly to mention, our oil submissions I used to teat would only ever pass the tests by at maximum the difference in documented certified testers. Each year organisations would send their raters/testers to a 3 day refresher course to ensure all raters gave the same results. Sort of a rater calibration workshop.
Anyway while I have very little MB knowledge so they may do things different the above is the normal certification procedure.
