Comments by "John Luetjen" (@jehl1963) on "Project Farm" channel.

You always do a very thorough job, but I've found an option that you didn't mention which works very well. This is especially true for engines, many of which have parts made of are iron, steel or aluminum -- and thus susceptible to oxidation with many cleaners. My car has a lot of aluminum and magnesium pieces -- which are both prone to oxidation. The solution that I found which works best is denatured mineral spirits. In addition to not oxidizing engine parts, it also tends to float the grime off of engines. I've found that many cleaners do dissolve the oil, but often leave the dirt behind in the form of a crusty, concrete type scale which can be difficult to remove. The mineral spirits on the other hand tends to rinse the dirt off with the oil. Maybe an option for a future test.
2