1. You shouldn't drink more than a gallon and a half of water per day very often. You won't get hurt, but if you drink, like, three gallons a day, you'll flush out electrolites and minerals your body needs.
2. Thanks for the tip! I didn't know oil could cleanse your mouth, but now that I think about it, of COURSE! It removes makeup. It would assimilate with the grime on your tongue and rinse it out! As for your question, I would say, consulting my deep well of ancient wisdom, (that was facetious) of course you can rinse your mouth out with oil. Just make sure you spit it all out, and spit out your saliva for awhile too, to make sure you don't drink any. Unless it's okay to drink some. I don't know if it is, so I'd say spit it all out, then rinse your mouth with water as hot as you can stand, or salt water as hot as you can stand. If you don't swallow any oil, why wouldn't you be able to do that?