mikesully02 wrote:
Read an interesting article lately in turbo diesel registry in which an engineer did a blind test for nearly every type of oil. Turned out the because of the detergents the CONVENTIONAL valvoline designed for Cummins is the best. I believe the best synthetic was rotella, with the fancy rip-offs coming much further down the list due to the fact that they contained almost none of the detergents used to actually hold the soot in suspension.
I am not so sure that this is true. The API is very particular on what is in an oil that is supposed to meet a certain classification. For instance, CJ-4. There has to be a certain level of detergents in the add pack to hold oil in suspension to meet the CJ-4 rating. Not so much in the CI-4+ rating that proceeded it. CJ-4 was designed to hold a lot of soot in suspension. Any oil that meets the CJ-4 would have the required level of detergents be it a conventional or synthetic base oil. A particular brand may have more detergents in the add pack than required by CJ-4, but that has to be balanced with the entire add pack to stay in compliance with API standards. You can't just throw in the base oil what you want and still meet specs. While it is true that the TBN rating of a lot of CJ-4 oils is lower than a lot of CI-4+ oils, that is due to the lower sulfur content of ULSD fuel compared to LSD. The acid control requirements are less. But it still has to maintain a high level of soot suspension capability. The Valvoline for Cummins you mentioned is interesting in that Cummins has a share in Ashland Oil which makes Valvoline. Darn good oil though. Shell (Rotella) makes the lion's share of base oil stocks for all the other brands in the country. Motiva (Shell) out of Port Arthur, TX is the largest base oil producer in the world and makes the bulk of base oil for the North American market. Infineum makes the add packs that go into Rotella, and likewise, they are the largest add pack producer in North America. Synthetic Group IV oils are made from Natural Gas by a number of producers.
When it comes down to it, almost all oils that meet the CJ-4 classification are virtually identical. The only difference is the base oil stocks. Mobil, Amsoil, Schaeffer, etc rely heavily on Group IV, while Castrol, Rotella, Pennzoil, Quaker State, etc rely on Group III synthetics which are produced by severly hydrocracked petroleum oil. The "conventional" oils rely on Group II and Group II+ base stocks.