A new heavy-duty engine oil category called PC-12 is set to launch January 1, 2027, and most of the coverage so far has been aimed at trucking fleets. For off-highway equipment manufacturers, your machines almost certainly don't need a different oil next year. The more useful question is what this on-highway transition means for how you spec engines, coordinate with lubricant suppliers and field questions from your dealer network over the next several years.
What PC-12 Changes
PC-12 was developed by the American Petroleum Institute to support on-highway engines meeting EPA emissions standards taking effect with the 2027 model year, which require substantially lower nitrogen oxide and particulate matter output. PC-12 requires further reductions in sulfated ash, phosphorus, and sulfur, the additive components that can degrade catalyst performance over time, along with the introduction of thinner XW-20 viscosity grades aimed to enable improved fuel efficiency in select on-highway engines. The category will be licensed as API CL-4, which replaces CK-4, and API FB-4, which replaces FA-4.
OEMs Should Be Watching
The EPA has long regulated on-highway and non-road diesel engines under separate emissions frameworks, and non-road requirements have historically taken years to catch up. When catalyst-based aftertreatment became mandatory for on-highway engines between 2007 and 2010, the equivalent non-road requirements didn't arrive until 2014 to 2017. That lag reflects a consistent regulatory pattern, and there's no indication that new requirements will move any faster through the non-road pipeline.
FB-4 is the clearest illustration of how narrow the current scope is. Its thinner xW-20 grades are only approved for use in certain on-highway engines, and no non-road engine on the market today accepts a fluid that thin. If your product line is entirely off-highway, FB-4 isn't a near-term consideration at all.
The real concern here is formulation drift, not compliance. Lubricant marketers generally don't build separate product lines for on-highway and non-road markets. When an on-highway specification changes, the products developed to meet it are typically engineered to remain suitable for the non-road engines already running on them. That means the reformulation happening now for CL-4 will, over time, show up in oils your engines are already spec'd to use, even though nothing in the non-road regulatory framework required it.
This has mattered before. Reduced phosphorus and thinner viscosity grades have historically drawn pushback from non-road engine builders, in part because duty cycles, ambient operating conditions, and durability expectations in off-highway applications differ meaningfully from on-highway use. If your engineering team has application-specific concerns about how a reformulated CL-4 product will perform in your platforms, particularly around wear protection or thermal stability under sustained load, this is the window to raise them with your lubricant suppliers.
CL-4 products were developed with backward compatibility as a design goal, meaning a single upgraded formulation is intended to serve new on-highway engines as well as legacy on-highway and non-road hardware already in the field, subject to individual OEM approvals. That intent doesn't remove the need for OEMs to confirm it for their own platforms. Ask your suppliers directly how they're validating CL-4 products against your current engine families, what testing supports that validation, and whether any of your spec sheets or owner's manual guidance will need updating as products transition.
Preparing Your Dealer Network for Customer Questions
Even though PC-12 doesn't require action on the non-road side, your dealers and service technicians are going to field questions about it, particularly from customers who read trucking-focused coverage and assume it applies universally. Equipping your service and parts network with accurate talking points now, before January 2027, will prevent a wave of unnecessary warranty inquiries or premature product swaps at the dealer level. The core message worth distributing internally is straightforward: named categories and product labels for many products in the market today will change, but current lubricant recommendations for non-road equipment remain valid unless your engineering team says otherwise.
If any part of your product line includes highway-capable or dual-rated equipment, such as new vocational trucks, delivery chassis, or road-legal support vehicles sold alongside your core off-highway lineup, those units are subject to the new requirements and on the same timeline as the broader trucking market. It is worth confirming internally which SKUs, if any, cross that line, rather than assuming your entire portfolio sits on the non-road side by default.
The Bottom Line for Off-Highway OEMs
PC-12 is a substantial shift, but the new products have been formulated to meet the needs of on- and off-highway engines, both new and old. The practical work between now and 2027 centers on staying engaged with your lubricant suppliers on formulation direction, confirming backward compatibility for your specific platforms, and making sure your dealer network isn't caught flat-footed by a customer question you could have answered for them in advance.
