The best engine oil additive to clean sludge is one that contains detergents and polymers dispersants. Detergents help break up the sludge particles, while polymer dispersants bind them together so they can be removed from your engine’s internals. This combination of ingredients helps keep your engine running smoothly by removing contaminants and restoring proper lubrication levels. Look for additives that include zinc dialkyldithiophosphates (ZDDP) as an anti-wear agent to provide additional protection against friction and wear. Zinc also helps protect against corrosion in older engines with higher sulfur content oils, which can cause deposits on sensitive parts such as camshafts and lifters. Additionally, look for additives containing molybdenum disulfide or boron compounds to improve the ability of the oil to cling to moving parts under high temperatures - this enhances overall protection from wear caused by heat build up. Lastly, consider adding an antioxidant ingredient such as Vitamin E which will help prevent oxidation damage over time due to long lasting exposure to oxygen in the air or fuel system components.