I seem to remember using a product marketed by Gunk as an engine cleaner about 40 years ago. It seemed like kerosene and came in a qt size tin can. Instructions said to add to engine oil and idle for 15 minutes. I recall that my 352ci Ford stalled around 5 minutes into the flush. I was concerned so I didn't restart to continue, so I changed my oil & filter. Seemed to due no harm nor did it seem to improve anything. I was a kid back then and the marketing worked its mojo on me.