Flexibility inherently exists in the fact that everyone involved in the production and distribution chain of each batch of fuel is presumptively liable, which will help to limit the occurrence of fuel that does not meet the 15 ppm standard (or other applicable designation).
A person fueling a vehicle at a retail outlet self-serve pump will not be liable for misfueling if the person does not cause the violation. For example, if the misfueling occurs because the retail outlet has mislabeled the pump stand or because the retailer or its distributor have contaminated the fuel with high sulfur product, the retailer and parties upstream may be liable, but the self-serve customer will not be liable unless it played some part in causing the violation.
However, if, for example, a person fuels a 2007 MY truck at a self serve pump labeled as dispensing 500 ppm fuel, the end user is liable.
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)