Over time normal engine operation and heat can cause polymer oil seals and gaskets to shrink, dry-out, become brittle and crack resulting in a minor oil leak. STP Engine Stop Leak is formulated to help stop minor oil leaks with a special agent to rejuvenate shrunken, dried out polymeric seals and gaskets. Plus, STP Engine Stop Leak helps fortify your oil with extra protection additives and a viscosity index improver. Compatible with regular and synthetic motor oils. Contains no solids to clog filters or inhibit flow. Will not harm oxygen sensors or catalytic converters.