I've seen several posts suggesting additives that go into the gas and oil, etc... One such item is ATF. I've heard that adding ATF to the crankcase will help keep the motor cleaner than oil alone. Is this true? How much to add? Should it only be done within 100 miles of an oil change? I've also heard of adding ATF to the gas tank, but I've no idea why. What good would ATF in the gas tank be? Good for carbs and bad for injectors?