you may have to register
[B]What about oil additives?
American Honda recommends against the use of any oil additives other than those already blended in the stock oil. Such supplemental additives are unnecessary when using quality oils displaying the Starburst certification symbol. Additives cannot prolong the life of a used oil, because the oil molecules have been broken down. The use of oil additives will increase your cost of ownership, and can lead to engine damage.
Does my Acura’s oil system require periodic flushing?
American Honda strongly recommends against this process, which is sometimes called “engine flushing.” Any engine damage resulting from this procedure will not be covered under warranty.
even though the newest synthetic formulations claim not to affect older engines, note the following doesn’t specifically mention new vs. old engines:
[B]What about synthetic motor oils?
You may use a synthetic motor oil if it meets the same requirements listed above. That is, it must display the Starburst symbol, and match the weight grade recommended in your owner’s manual.
When using synthetic oil, you must follow the oil and filter change intervals given in the maintenance schedule