Is Cylinder Scoring Related to Using 40-Grade Engine Oil?
2 Answers
Cylinder scoring has some relation to using 40-grade engine oil, but it's not an absolute cause. The relationship between cylinder scoring and engine oil: Improper selection of oil viscosity, incorrect oil grade selection, excessive oil contaminants, air filter failure, and other factors may contribute to cylinder scoring. However, the likelihood of cylinder scoring caused by poor oil quality itself is minimal, and it has little to do with the oil's inherent quality. Main causes of cylinder scoring: Insufficient clearance between piston and cylinder; piston ring breakage or seizure on the piston; piston pin circlip breakage or detachment; poor engine cooling or cooling system malfunction; prolonged overloaded low-speed driving; piston and piston ring tilting to one side and pressing tightly against the cylinder wall are the primary causes of cylinder scoring.
It depends on the specific vehicle condition. Having repaired cars for so many years, I've seen many cylinder scoring cases where using 40 viscosity oil could indeed be one of the contributing factors. New car engines have smaller clearances - if 40 oil is too thick, the oil film forms slowly during cold starts, causing dry friction between piston rings and cylinder walls that leads to scratches. Just last week I repaired a German car where the owner had been using 40 oil consistently, and upon disassembly we found three scoring marks on the cylinder walls. However, cylinder scoring is usually a comprehensive issue - besides incorrect oil viscosity, factors like insufficient high-temperature protection, cooling system failures, or prolonged low oil level operation can also contribute. The safest approach is to follow the maintenance manual's recommended viscosity and regularly check oil pressure and the cooling system.
