Cummins is revising its rollout of Model Year 2027 on-highway diesel engines following the Environmental Protection Agency's proposal to ease some of the implementation requirements for its 2027 emissions rule.

As Heavy Duty Trucking reported earlier this month, the EPA proposed giving engine manufacturers more flexibility in how they transition to the new standards while keeping the stricter nitrogen oxide (NOx) emissions limits in place.

Based on the proposal, Cummins said it plans to use those implementation flexibilities to make what it calls a "measured transition" to its new HELM engine platforms.

The new X10 and X15 are part of Cummins' fuel-agnostic HELM engine platform, which is designed to accommodate multiple fuel types while meeting future emissions requirements. Cummins said the diesel versions will offer improved fuel economy, similar diesel exhaust fluid consumption and reliability.

Why a Phased 2027 Engine Rollout?

Cummins said the phased rollout is intended to maintain regulatory compliance, support OEM production schedules and give the company more time to ramp up manufacturing while ensuring product quality.

The phased rollout means OEMs and fleets will continue to have access to current-generation engines while Cummins gradually introduces its new 2027-compliant products.

Cummins said the updated launch schedule is based on its current understanding of EPA's proposed rule. The company said it will adjust its plans if the final regulation differs significantly from the proposal.

“Our long-term product strategy has not changed,” said Cummins CEO Jennifer Rumsey. “This is about improving the transition, not changing the destination.

"A phased production ramp will allow us to support customers while building confidence in our new products through real-world operation and maintaining our focus on quality.”

Cummins Slows X15 Rollout

Cummins plans to begin limited production of the Model Year 2027 X15 in January 2027, depending on individual OEM launch plans. Production will gradually ramp up, with full production expected in the fourth quarter of 2027.

During the transition, Cummins expects its current-generation X15 engines to remain available.

X10 Production Ramps Through 2027

Cummins plans to begin limited production of the Model Year 2027 X10 engines in January 2027, with full production expected by the third quarter, depending on OEM launch schedules.

During the transition, the current X12 and L9 engines used in truck and transit bus applications are expected to remain available.

Next-Generation B Platform Remains on Track

The company said its next-generation B platform is still expected to launch in January 2028.

The current B6.7 will remain available through 2027 to support customer production schedules and ensure a smooth transition to the new platform.