정 불안 하시면 stp, Lucas 등 에서 나오는 high mileage 오일 첨가물을 넣으 십시요.
"Since most additive packages appear to be quite similar, it can be difficult to distinguish any real differences between many engine oils. Even with high mileage oils, the additives don’t seem to vary much at all."
https://www.machinerylubrication.com/Read/31414/high-mileage-oil