Quick answer
Mixing different brands of engine oil additive can lead to chemical conflicts or over-lubrication. If you want multiple benefits, pick a single, reputable product designed for all your needs.
Detailed answer
Each additive brand has its proprietary formula, often with carefully balanced detergents, friction agents, or seal conditioners. Combining them can overload certain components—like friction modifiers—causing the oil’s viscosity or anti-foam properties to go haywire. You might end up with deposit formation or inoperative seals. If you must address multiple issues (like leaks and sludge), look for a product that explicitly tackles both, or treat them sequentially: one additive per oil cycle. This approach avoids potential chaos from mixing multiple unknown chemistries.
