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.