Tim,
Having sold Castrol Industrial lubes in India for over 17 years I feel selling additives is the a much tougher job and you have lot of work ahead of you.
From what I know, Lubrizol, Ethyl, Infenium are the top Engine oil additives in use in India and I am sure they would be among the top five in US as well. The main choice is brand; service and price thereafter.
As far as introducing new additives are concerned I would like to share my experience of the 90's. Castrol Marine introduced a new range of oils for use on auxilary engines on board and on land for use on Diesel Generating sets. Wartsila ( in India) one of the leading marine engine manufacturers made a racket; and demanded a complete set of performance tests and 10,000 hrs plus endurance tests prior to use by its customers. Fortunately Castrol had been doing series of test worldwide prior to its launch and was able to support its claims.
The fact of the matter that many OEM's "delist the approval" if there is a change of blend or formulations in the "approved" lube oil.
Tim, if I were a quality conscious Technical/QC manager of a Lube company I would not accept your samples. I would ask you to conduct and pay for the series of performance test (like various API - CF4 tests in toto.) and simultanously run endurance tests. All this would take months and months and only after satisfactory performance would I agree to use your product. There would also be another little test of compatibility with other additive pcakages in the "formulation." After all this, I may still have to seek re-approval from (say GM) for the (say CF4 Engine oil.)
On the other hand, smaller and growing companies may take the challenge and use a newer product at face value. That then, should be your target. And after establishing yourself, you can approach the bigger brands.
Hussam Adeni