Have any of you freeloaders heard of the ongoing oil crisis on the planet!? What a waste of oil. I'm not a big tree-hugger or anything, I never intend to buy an electric car, blah blah blah, but this is an example of a really stupid idea. It is a fact that this world will run out of oil in my child's lifetime, and I'm only 26. Now I can hope for her sake that the powers that be come up with a good substitute by then (science is an amazing thing), but to have you waste it for the satisfaction supposedly cleaning out your engine is ridiculous.
BTW, it's not going to do anything for your engine. Consider this. If your car has a bunch of mud caked on the rocker panels, does pouring a couple gallons of water on that mud remove it? No. If you can't see out your windshield, would just squirting washer fluid on it work? No, you have to wipe that off. Any deposits on your engine (which are few if any) are not going to be rinsed away by 4-5 quarts of anything sloshing around in there for a mile.