Tier 3 is an Environmental Protection Agency (EPA) program regulating fuel efficiency in cars and the sulfur content of gasoline. Together, these rules will reduce the harmful emissions created by cars and help clean the air.

While all cars model-year 2017 and newer are phasing in Tier 3 efficiency standards (with full compliance expected by model-year 2025), not all gas refiners are currently producing Tier 3-compliant fuel: while some refineries in the area produce low-sulfur, Tier 3 gas which will clean the air, others comply with the Tier 3 regulations through corporate-scale averaging or buying credits from other refineries. To find out which brands and gas stations sell Tier 3 gas, see our “Where to Buy” page.

Used with fully compliant Tier 3 vehicles, this cleaner gas will reduce up to 80% of key auto emissions that contribute to ozone and particulate pollution. When used with older vehicles, key emissions reduction is typically 13%. Although this may not sound like much, it is comparable to not driving for one day every week! Cleaner air protects the public health and reduces harm from heart and lung diseases.

You can read more about EPA’s Tier 3 rules on the EPA website or on our FAQ page.