The proposed rule, which still is under wraps, is awaiting final review at the White House Office of Management and Budget.
Last May the agency said it would allow Navistar to pay non-compliance penalties. Navistar said it needed that relief in order to keep selling its Class 8 engines, which use an exhaust gas recirculation technology that has not yet been able to bring the engines into compliance with clean air requirements.
Normally such a decision by EPA would require a formal notice and public comment, but the agency invoked a "good cause" exception that allowed it to grant the penalties without going through the comment period.
But competing engine manufacturers objected to EPA's approach, and won a court order that said the agency should not have allowed the penalties without going through notice and comment.
The proposal that is now at OMB presumably will begin the notice and comment process.
Meanwhile, Navistar has decided to start using the urea-based aftertreatment technology that the other engine manufacturers use to meet clean air standards.