BS2 v/s BS3
Well, starting off with my answer… initially, I am anxious to know what exactly this “BS” stands for… thus, this stands for “Bharat Stage” a standard for emission, which is speaking out loud its story… So post the number placement of BS, states its “Stage Number”.
Now talking about your query, stating the difference between BS2 and BS3 engine or let’s go a bit advance for that matter by including the BS4 deals with the standard of an emissive composition of the fuel.
The few of the major differences that one should be aware of:
The emission from this type of engine contains Sulphur content of 0.5 g/kg and Lead content is 0.013g/liter.
The emission from this type of engine contains Sulphur content of 150 mg/kg (for gasoline),
350 mg/kg (for diesel) and Lead content is 0.005 g/liter.
Clearing off with your doubt about India, currently, India is following BS4 as standard. But, later in future by 2020, Indian Government are planning to go ahead with BS6 engine intends to skip the BS5 engine.