Wandering off the OP's subject, but about a dozen years ago, my mom bought a lawn mower from a farm chain store. The salesman swore to her up and down that you MUST use non-detergent in her new lawn mower. If she didn't, HER WARRANTY WOULD BE VOID was what he brainwashed into her head. She purchased some non-detergent oil for her next oil change.
She then thought I was missing a few marbles when she told me that I would being non-detergent oil when I changed oil in her mower for the first time. I quietly opened up the operator's manual and pointed out what the factory said her lawn mower needed. She got quiet after that and took the oil back the next time she went into that store. I just wonder how many other customers used non-detergent oil for the life of their mower?