The 2 ppm downstream sulfur test tolerance (§ 80.580(d)) applies at all locations downstream of the refiner/importer beginning on October 15, 2008. Prior to that date, a 3 ppm test tolerance adjustment applies at these locations.

Question and Answer was originally posted at Questions and Answers on the Clean Diesel Fuel Rules (PDF)(135 pp, 888 K, EPA420-B-06-010, July 2006, About PDF)