I always thought bon ami was for seating rings.
It's very funny that you'd bring that up. What I was told is that in the early 60's cat diesels (sp) had just started using a hard chrome ring that didn't seal well after the engine was assembled. A tech at one of the dealers was taking Bon Ami cleanser and putting a table spoon or 2 in the engine which was helping the rings seat. Bon Ami is one of the least expensive cleaners on the market now and it works really good, but if you go into any cat dealer you can still get "ring seating matereal" from them and it's around $10 a can, which is the same size as a normal Bon Ami can.
