Don't ever touch it. Slick 50 was fined by Federal Trade Commision for false advertisement:
"The Federal Trade Commission has charged Quaker State - Slick 50, Inc., the manufacturer of Slick 50, the best-selling auto engine treatment in the U.S., with making false and unsubstantiated advertising claims. According to the FTC, ads for Slick 50 that tout tests showing improved engine performance are false and its claims of reduced engine wear are unsubstantiated."
A friend of mine changed his oil every 3k on his 2000 Montero and always put in the dealer recommended oil additive, at 70k he was getting a slight ticking that was getting worse and worse so he took it in and the dealer sent his engine out to be clean/washed and rebuilt: seems the dealer additive was like putting a small bottle of tar in each oil change that was slowly coating the entire engine, it looked like tar with crystals in it
All these additives do nothing except fatten the wallets of the people who own/run these Corporations, some additives like a fuel injector cleaner that is tried and tested is OK but for these new cars that are generally maintained and not neglected I would stray away from using your ride as a test mule.
Slick 50 does work but for cars on their last leg, it's like pouring several shots of 75w oil into an engine that burns more oil then gas:arrow:
Slick50 is snake oil and causes teflon buildup in the engine. Just run a quality synthetic oil and change regularly and your motor will last you years and years.