a standard spark plug should last 10-20K KM...those better/performance type should last 30-50KM....
Spark plug is wear and tear part...
Also life span of spark plug depend on your engine condition...if your engine makan engine oil / wrong tuning then your spark plug will wear out faster.
While traveling at 140km/ph, car was under power n was vibrating . Its like 'semput' when pressing the pedal. Slow down was fine ,press the pedal /floored to max ,rpm doesn't goes high . Could this cause by steeper...