FWIW, I leave mine in the solution for 24 hours. As long as the entire engine is covered it comes out looking pretty clean. Any uncovered part turns an ugly dark gray color.
. . .
Alan --
Well I'll be! I've heard people complain about the "ugly dark gray color" (I've never had that problem), but never heard a logical explanation before. Makes sense.
My big, strong, handsome wife taught me crockpot techniques, and she dunks the bird deep, like an enthusiastic Baptist. What's good for chickens is good for Foxes, right? (or some metaphor I forgot, foxes, chicken coops, something)
My experiences have been good -- 24 hours, Prestone premium "Long Life", full strength, never any problems, never any residue that wouldn't come off with mild brushing.
Larry Fulwider