edgeoftime
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This is the problem with additives - there are no independent long term test results available and the people using them are the guinea pigs. At best you can hope for a tiny little bit of improvement, a good result is just that no damage is done, but if your engine is knackered then that's tough luck.
I still remember when Slick 50 was the thing everyone should use - it turned out to be expensive snake oil with a hint of Teflon that can build up and restrict oilways.
That stuff "did" for my BMW R50. never again will I add anything to any engine unless the maker says ok.