The prebuy that did and did not happen

A prebuy is what fleets do before an expensive rule takes effect: order the old, cheaper truck while they still can. The last big one, in 2006, pulled a year of demand forward and then left the factories idle. The 2027 federal rule on nitrogen oxides, which requires a cleaner and dearer engine, was expected to do the same. Read the September headlines and you will find two claims that seem to contradict each other.

The first: FTR reported that orders for 2026 were running more than double 2025, that the factories' second-half build slots were oversold by about 35,000 trucks, and that the surcharge-free slots were "likely filled", bringing the prebuy "effectively to an end". The second, from FleetMaintenance a week earlier: "the anticipated pre-buy did not materialize as expected."

Both are true

They measure different things. FTR is describing build-slot availability: relative to what the factories could make, demand was oversubscribed, and by Labor Day, FleetOwner reported, "all remaining 2026 prebuy options were exhausted." FleetMaintenance is describing scale relative to history: relative to 2006, fleets did not stampede. ACT Research's phrase splits the difference: "a selective and uneven pull-forward rather than indiscriminate purchasing."

The reason is the price of compliance. A few years ago the 2027 engine was expected to add 20,000 to 25,000 dollars to a new truck. The figure that emerged is 8,000 to 12,000 dollars for a fully compliant engine, or a non-compliance penalty engine at roughly 6,000 to 7,000 dollars instead. The rule itself, 35 milligrams of nitrogen oxides per horsepower-hour, still stands; what the EPA proposed in July 2026, with comments closed on 29 August and no final rule yet, is to make those penalty engines available from model year 2027 and to soften the warranty and useful-life terms. When the cliff is smaller, fewer fleets jump early. Fleets with financing and a replacement need pulled orders forward. Everyone else waited.

What it does to used prices

Two forces, pulling in opposite directions on different trucks. The first is a ceiling that rises. A new truck costs more from model year 2027, and the 25 percent tariff on imported medium and heavy trucks and parts, in force since October 2025, adds more still. ACT's Steve Tam has said used prices run in "a tight band of about 30 to 35 percent of the new truck price", so a higher ceiling lifts late-model used values with it.

The second is a wave. Every truck ordered in 2026 and delivered in 2027 replaces a truck in a fleet, and that truck, typically four to six years old, becomes a trade-in. It lands in the used market six to nine months after the new one is ordered. Today that cohort is scarce; J.D. Power spent a year noting that "lower-mileage trucks remain scarce and continue to bring premium money." Its September 2026 edition turned the page: "Expect to see more three- to five-year-old sleepers returning on trade as customers take delivery of an increased number of new trucks in upcoming months," and "the 2027 model year has been backloaded ... This positions customers for elevated volumes in the fourth quarter." The wave has a date now.

Expect a split, not a move: the late-model market loosens in 2027 while older cohorts stay supported by a dearer new truck and steady exports.