In my decidedly biased opinion, oil additives are sucker bait, for the most part. The only times I've been successful with an additive is doing a heavy overdose of a lightweight solvent like kerosene or Diesel fuel to flush sludge out of a badly gunked-up engine. Run the mix for about 20 or 30 minutes at fast idle and don't put any driving load at all on the engine. Then drain and refill with fresh oil. The heavy additives like "Motor Honey" or STP just don't make much sense to me. A little Marvel Mystery Oil to free up a sticky hydraulic lifter might be OK, but I've never seen one of the "overhaul in a can" treatments do much good in the 50-something years I've been tinkering with engines.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!