Based off my experience in law enforcment, I'd say "NO"! We have cars that sit at idle for hours, others that go from cold to 5.5K rpms in a few seconds...over and over and over. And I've never blown a motor...EVER. I've run chevy, ford and dodge...and none of them ever got snake
oil, and none of them were retired before 150K (then sent onto the next agency to drive another 100K), and none had any major engine failures. Having torn down a couple of my personal engines, I'd say the best thing is to just change the
oil every 3K and use good gas (carbon build up seemed highest when I used Shell gas, Chevron doesn't seem to leave as much on the valves).
The only thing I've seen burned up is trannies, brakes and tires. For the record, police use regular
oil and the cheapest gas on the planet. Do I think some of those products might do something...sure, but considering thousands of law enforcement and military vehicles go without the stuff with no problems, why waste the money???