The recommended usage info direct from the Mfg. website:
http://www.royalpurpleconsumer.com/p...ystem-cleaner/
RECOMMENDED TREAT RATE & USAGE
3,000 MILE INTERVAL 6 OZ. CAN
Pour entire contents of 6 oz. can into tank prior to fueling. Treats up to 20 gallons. Ideal for two and four stroke engines.
10,000 MILE INTERVAL 20 OZ. CAN
Pour entire contents of 20 oz. can into a nearly empty tank and refuel. One (1) can treats up to 20 gallons. For tank sizes outside of this range, use one (1) ounce per gallon. In two-cycle engines, use one (1) ounce per two (2) gallons.