UOAs are certainly a good guideline, but they cannot give all the answers in matters of formulation changes. For example, the elemental analyses will give ppm amounts of the different elements such as Zinc (Zn), Barium (Ba), Calcium (Ca), etc. which may be identical, but they do not tell you what the "organo" portion of the organometallic ingredient was. If a company decides to make a change in the additive package for reasons of cost, supplier source, etc., any change can impact how the resultant additive package functions. In theory, any change in additive ingredients should necessiate full engine retesting unless the company can assure itself that such changes would not impact the overall performance. In practice with all pushing to have higher profit margins, the retesting may fall by the wayside. That is some or part of the rationale for why API has their certification and an approved formuale/recipe once certified.
