Q. Using BS4 fuel in BS6 has any implications on engine's wear and tear ?

BS IV fuel has a higher sulphur content of 50ppm(parts per million) and BS VI fuel is more refined containing only 10ppm(parts per million) sulphur.So if BS IV fuel will be used in a BS VI engine it will clog the fuel filter much before the scheduled fuel filter replacement time affecting the fuel flow to engine hence affecting engine performance and consequently increasing fuel consumption.The secondary effect is damage to the catalytic converter which converts the unburnt hydrocarbons,carbon monoxide to carbon dioxide and water thereby reducing the emission fooprint.A damaged converter has reduced efficiency of doing its work of reducing emissions.Hence it is not advisable in the long run to put BS IV fuel in BS VI engines.Hopes this helps.

For optimal results, BS6-compliant engines will have to run on BS6 fuel, as new-generation engines running on lower quality fuel will emit a quantum of toxic gases comparable to that generated by BS4 engines. Moreover, running BS6-compliant vehicles on BS4 fuel could be detrimental to their engines.

BS VI IS MORE REFINED. USING BSIV FUEL WILL REDUCE ENGINE LIFE , WILL INCREASE MAINTENANCE AND GIVE POOR PERFORMANCE