Difference between euro 3 and 4 engine?

Euro 3 and Euro 4 are emissions standards set by the European Union to regulate pollutants from vehicle engines. Euro 4, which came into effect in 2005, imposes stricter limits on nitrogen oxides (NOx) and particulate matter compared to Euro 3, which was implemented in 2000. This means that vehicles meeting Euro 4 standards typically have improved emission control technologies, leading to cleaner exhaust and reduced environmental impact. Consequently, Euro 4 engines are generally more efficient and environmentally friendly than Euro 3 engines.