European emission standards commonly known as Euro standards are used to define the acceptable limits for exhaust emissions of vehicles that are currently in use. These so called emission standards are defined in a series of European Union (EU) directives staging the progressive introduction of increasingly stringent standards.

The dates below are the implementation date for new vehicle type approvals. The dates in brackets are the implementation date for all new vehicle registrations, normally one year later, so a car registered between the two dates may meet the corresponding emissions standard and a car registered after the date in brackets will meet it.

Euro 1 Standard (EC93)

July 1992 (January 1993)

The introduction of the Euro 1 standard in 1992 required the switch to unleaded petrol and the universal fitting of catalytic converters to petrol cars to reduce carbon monoxide (CO) emissions.

Euro 1 emission limits

CO – 2.72 g/km (petrol and diesel)
HC+ NOx – 0.97 g/km (petrol and diesel)
PM – 0.14 g/km (diesel only)
Euro 2 Standard (EC96)

January 1996 (January 1997)

The Euro 2 standard further reduced the limit for carbon monoxide emissions and also reduced the combined limit for unburned hydrocarbons and oxides of nitrogen for both petrol and diesel vehicles. 

Euro 2 introduced different emissions limits for petrol and diesel.

Euro 2 emission limits (petrol)
CO – 2.2 g/km
HC+ NOx – 0.5 g/km
PM – no limit
Euro 2 emission limits (diesel)
CO – 1.0 g/km
HC+ NOx – 0.7 g/km
PM – 0.08 g/km

Euro 3 Standard (EC2000)

January 2000 (January 2001)

Euro 3 modified the test procedure to eliminate the engine warm-up period and further reduced permitted carbon monoxide and diesel particulate limits. Euro 3 also added a separate NOx limit for diesel engines and introduced separate HC and NOx limits for petrol engines.

Euro 3 emission limits (petrol)
CO – 2.3 g/km
HC – 0.20 g/km
NOx – 0.15
PM – no limit
Euro 3 emission limits (diesel)
CO – 0.64 g/km
HC+ NOx – 0.56 g/km
NOx – 0.50 g/km
PM – 0.05 g/km
Euro 4 Standard (EC2005)

January 2005 (January 2006)

Euro 4 (January 2005) and the later Euro 5 (September 2009) concentrated on cleaning up emissions from diesel cars, especially reducing particulate matter(PM) and oxides of nitrogen (NOx).

Some Euro 4 diesel cars were fitted with particulate filters.

Euro 4 emission limits (petrol)
CO – 1.0 g/km
HC – 0.10 g/km
NOx – 0.08
PM – no limit
Euro 4 emission limits (diesel)
CO – 0.50 g/km
HC+ NOx – 0.30 g/km
NOx – 0.25 g/km
PM – 0.025 g/km
Euro 5 Standard

September 2009 (January 2011)

Euro 5 further tightened the limits on particulate emissions from diesel engines and all diesel cars needed particulate filters to meet the new requirements. There was some tightening of NOx limits too (28% reduction compared to Euro 4) as well as, for the first time, a particulates limit for petrol engines – applicable to direct injection engines only.

Addressing the effects of very fine particle emissions, Euro 5 introduced a limit on particle numbers for diesel engines in addition to the particle weight limit. This applied to new type approvals from September 2011 and to all new diesel cars from January 2013.

Euro 5 emission limits (petrol)
CO – 1.0 g/km
HC – 0.10 g/km
NOx – 0.06 g/km
PM – 0.005 g/km (direct injection only)
Euro 5 emission limits (diesel)
CO – 0.50 g/km
HC+ NOx – 0.23 g/km
NOx – 0.18 g/km
PM – 0.005 g/km
Euro 6 Standard

September 2014 (September 2015)

The Euro 6 standard imposes a further, significant reduction in NOx emissions from diesel engines (a 67% reduction compared to Euro 5) and establishes similar standards for petrol and diesel.

Exhaust Gas Recirculation (EGR) – replacing some of the intake air (containing 80% nitrogen) with recycled exhaust gas – reduces the amount of nitrogen available to be oxidised to NOx during combustion but further exhaust after treatment may be required in addition to the Diesel Particulate Filters required to meet Euro 5.

Euro 6 diesel cars may also be fitted with:

  • A NOx adsorber (Lean NOx Trap) which stores NOx and reduces it to Nitrogen over a catalyst
  • Selective Catalytic Reduction (SCR) which uses an additive (Diesel Exhaust Fluid (DEF)) containing urea injected into the exhaust to convert NOx into Nitrogen and water.
  • The use of Cerium, a fluid injected into the fuel tank each time the vehicle is refuelled which assists the DPF regeneration by lowering the temperature needed for regeneration.
Euro 6 emission limits (petrol)
CO – 1.0 g/km
HC – 0.10 g/km
NOx – 0.06 g/km
PM – 0.005 g/km (direct injection only)
PM – 6.0×10 ^11/km (direct injection only)
Euro 6 emission limits (diesel)
CO – 0.50 g/km
HC+ NOx – 0.17 g/km
NOx – 0.08 g/km
PM – 0.005 g/km
PM – 6.0×10 ^11/km