European Union regulations, published as Directives, have the force of law within EU member states under the provisions of the Treaty of Rome. With the introduction of the "Consolidated Emissions Directive" in June 1991, implementation became mandatory for all EU member states and was no longer left to the discretion of individual nations.

In cooperation with the oil and motor vehicle industry, the Commission devised a common "Auto-oil Programme" to reduce exhaust gas emissions. The Auto-Oil Programme features two new Directives (98/69 and 98/70 amending Directives 70/156 and 70/220) dealing with the quality of petrol (gasoline) and diesel fuel and measures to tackle air pollution from vehicle emissions.

Directive 98/70 introduces new environmental specifications applicable to petrol and diesel fuels, and it bans leaded petrol from the market from the year 2000. It also provides for progressive improvements in the environmental quality of unleaded petrol and diesel fuel.

Directive 98/69 lays down differing limit values for emissions by petrol and diesel cars from 2000 to 2005. The Directive also permits tax incentives to be granted by Member States to encourage advance compliance with new limit values.

Directive 98/77 inserts new technical requirements into Directive 70/220 such as the EC approval of replacement catalytic converters as separate technical units, the EC approval of vehicles which may operate on LPG or CNG, and the measurement of rolling resistance.