Feb 08, 2014 · After 10,000 km High Mileage Deterioration starts eating away at the car’s stock HP and will be noticeable by 12,837 km. The following shows that the High Mileage Deterioration will be applied after Oil and Engine Deterioration have already been applied to the Stock HP: OIL + OIL/ENGINE (5000 km to 5300 km) + (5300 km to 5974 km) 24 + 59 = 77 ... I don’t really know that they were actually any worse than the other brands of 10w40 oil or not, in fact I don’t think they were any worse at all. Times have changed, oils have improved, I guess even the 10w40 oil of today, and engines are better designed so the oil doesn’t run quite that hot, but I still will not use 10w40, any brand.