John :
1)In crankcase 1 week prior to oil change, 2/3rds a bottle for smaller engines entire bottle for large engines.Its thins the oil out some so its best to add it to a xw-40 rather than a xw-30 weight oil.Most of it will evaporate out within less than a week.You keep it in longe,r some of the varnish it dissolved in the oil may re-deposit again in your engine.
2)Yes, you can just add a bottle to gas tank (if its full)
Fred...
