You know that feeling at the top of a roller coaster's first hill.

The chain lift has been clanking for what feels like forever. You're strapped in. There's no getting out now. You look down the track — and about a hundred feet ahead, there's a section that just... isn't there yet. A couple of guys in hard hats are still bolting it together. And over the loudspeaker, a cheerful voice crackles:

Welcome to the 2027 heavy-duty engine transition.

I've been in the truck business a long time. I've ridden the 2007 coaster and the 2010 coaster, and I've still got the receipts from both. But I have never — never — seen the industry board a ride like this one, where every OEM on the midway is waving us toward the loading platform, assuring us the track is complete, while their own engineers are visibly still welding on the far turn.

So today I want to do two things. First, I want to walk you down the midway and show you exactly what each ride operator is saying right now — with sources, because at RDK we don't do rumors. Second, I want to give you a calendar. Because most businesses remember these days: the days an OEM looked us in the eye and told us the engines were ready. Pin this calendar to the shop wall. We're going to want it later.

Why I'm Writing This — A Wake-Up Call, Not a Rock

Before we walk the midway, let's get one thing straight about who's talking and why.

This letter comes from me — Richard Kemner. I own RDK Truck Sales, and this is not a rock being thrown at the OEMs. Every engine maker in this letter is doing exactly what most companies in America are doing right now: trying to survive. A rulebook this size, changing this fast, doesn't leave a manufacturer many good moves — phase the launch, soften the warranty, keep the current engines selling. Sitting in their boardrooms, I'd probably make the same calls.

And the EPA? The EPA had a good intention. Cleaner air isn't something anybody in this business argues against — we live behind these exhaust stacks all day. But somewhere between the good intention and the loading dock, the weight of it landed on hardworking people: the hauler with six trucks, the municipality on a fixed budget, the owner-operator whose truck is his retirement plan. Stress and financial consequences, falling on the folks least able to absorb them.

Is it global warming? Is it government regulation? Or is it something in between? I'm not going to settle that argument in a truck letter, and I don't need to. What I can do is make sure everyone — customer, friend, competitor, anybody who's survived the last 25 years of this industry — has the right to be knowledgeable about what's happening. That's the whole mission here: information, out in the open, with sources.

And understand: I'm not watching this ride from the fence. RDK bets its own future on this market every single day. These decisions will affect us too, and here's one effect we can already see coming: used truck prices are going up. When new trucks get more expensive and less proven at the same time, everybody runs to the proven trucks — and the price of proven trucks climbs. In the long run that squeezes a lot of smaller companies, and history says some of them will be forced out, or forced to sell. That's not a sales pitch. That's the weather report.

So read what follows the way it's meant: a wake-up call. Not panic — preparation.

The Chain Lift: How We Got to the Top of This Roller Coaster Hill

The rule itself hasn't blinked. EPA's heavy-duty NOx standard — 35 milligrams per horsepower-hour, roughly an 80% NOx cut — still takes effect January 1, 2027. That part of the track is bolted down tight.

What happened in July is that EPA walked out onto the platform and loosened everybody's harness. On July 9, 2026, the agency proposed a new rule (EPA fact sheet, Federal Register, July 14, 2026) that keeps the 35 mg NOx limit and the 2027 start date but softens nearly everything around it:

• The emissions warranty stays at five years / 100,000 miles instead of ballooning
• The longer useful-life requirements get pushed to model year 2030
• Those dreaded DEF speed-and-power derates get replaced with dashboard warnings on new builds
• And — read this one twice — EPA would allow nonconformance penalties, meaning manufacturers can temporarily sell engines that don't fully meet the standard while they finish the transition (Heavy Duty Trucking)

EPA says this saves the industry $12 billion and up to $6,000 per truck (EPA news release). Fine. But friends, think about what a nonconformance penalty actually is. It's the ride operator saying: "Some of the cars might not have all their wheels, but we'll pay a small fine for each one, and the line keeps moving."

Back in May I told you the warranty dollars were the tell — that the truck makers were showing us how nervous they were about these engines by how much money they were setting aside to warranty them. Well, the sequel is even better. EPA just proposed letting them warranty these engines less and sell them before they fully comply. If the 2027 engines were as ready as the press releases say, nobody would need either of those escape hatches.

The Drop: Cummins Grabs the Brake Lever

And then came the most honest moment of this entire transition.

On July 23, 2026 — exactly two weeks after EPA loosened the harness — Cummins announced a "phased Model Year 2027 product launch plan" (Cummins investor release):

• X15: limited production January 2027, full production Q4 2027
• X10 — the engine that matters most to every refuse and roll-off operator reading this: limited production January 2027, full production Q3 2027
• Next-generation B platform (B7.2): pushed all the way to January 2028, with the current B6.7 staying available through 2027

CEO Jennifer Rumsey said the phased ramp will let Cummins support customers while building confidence in their new products through real-world operation (Heavy Duty Trucking).

That real-world operation hasn't happened yet. That cheerful voice on the loudspeaker just told you exactly who the test ride is. It's the early buyer. It might be you.

Now — credit where it's due. Cummins grabbing the brake lever and phasing the launch is the responsible move. I'd rather ride with an operator who slows the train than one who pretends the track is done. But let's not kid ourselves about what it means: the company with the most vocational skin in the game just told us their own engines need a year of seasoning after launch before full production. That's not the sound of "ready." That's the sound of "getting there."

Walking the Midway: What Every Ride Operator Is Telling You

Here's the state of every coaster on the fairgrounds, as of this week. Every claim sourced, because that's how we do it.

Cummins — Phased everything, as above. The X10, replacing both the L9 and the X12, is the refuse, dump, and mixer diesel going forward, running a 48V system with electrically heated twin-module aftertreatment (Autocar). Full production Q3 2027 — that date, not January, is when vocational volume actually arrives. The natural gas L9N and X15N carry on as the proven alternative fuel play.

Mack — The only OEM in the industry with a confirmed 2027 order bank: the new MP13 opens for orders August 2026, production timed to model year 2028 (Transport Topics). And here's a structural change that matters enormously to our world: the MP7 and MP8 are being sunset. The TerraPro moves to the Cummins X10; the Granite gets MP13 or X10 (Trucking Info). And the LR refuse chassis? Mack's own page still shows no 2027 engine information at all (Mack LR Series). The refuse car on this coaster doesn't have a seat assignment yet.

Detroit / Freightliner / Western Star — The steadiest track on the midway, at least on paper. DD13 and DD15 Gen 6 hold their January 2027 production date, DD16 follows in January 2028, and Detroit gets to 2027 compliance with a pre-SCR stage — no electric heaters, no 48V system, and back-of-cab equipment, wheelbases, and body configurations unchanged (Freightliner). For body builders and upfitters, that's the least re-engineering of anybody. Still no order-bank date or pricing published, though. Steady track — but nobody's ridden it either.

Volvo — The 2027 D13 was unveiled at ACT Expo in May with dual SCR and electric heaters (Volvo Group), but Volvo itself has published no order-bank date. The one to watch: their all-new vocational truck, code-named "X," launching Q3 2026 and covering everything from mixers to refuse (Transport Topics). That reveal is weeks away.

International — The quietest car on the train. Their pitch since January has been that the 2027 S13 carries over more than 90% of existing hardware backed by 700+ million fleet miles (International press release) — the "our coaster is really the old coaster with new paint" argument, and honestly, it's not a bad one. But their stated "mid-2026" availability estimate has now come and gone with no confirming announcement (Transport Topics). Mid-2026 was last month, fellas. We're all standing here holding our tickets.

PACCAR (Kenworth / Peterbilt) — The ride behind the curtain. In February they teased two all-new engine platforms, tested in the Arctic Circle and Death Valley, with details promised "later this year" (Transport Topics). Five months later: no names, no specs, no dates, no order banks. The Peterbilt 520 refuse chassis page still lists only current engines (Peterbilt). You can hear the coaster running behind the curtain. Nobody's allowed to see it.

The Test Ride Nobody Mentions

Here is the single most important fact in this entire letter, and I want it in bold.

One truck. At a trade show. With a factory test driver at the wheel.

No customer fleet is running these engines. No refuse route has one. There is zero real-world refuse duty-cycle data — no stop-and-go, no low-load cold mornings, no packer-cycle PTO abuse, no hundred-stops-a-day reality that our industry lives in. And stop-and-go refuse duty is precisely the application where heated aftertreatment systems will be stressed the hardest.

The market has done the math. June Class 8 net orders came in around 31,400 units — up 231% from last June and 68% above the ten-year average (FleetOwner). That's not an order board. That's the entire industry sprinting for the pre-buy exit before the coaster leaves the station. Build slots for proven, current-emissions trucks are the scarcest commodity in trucking right now, and they're getting scarcer every week.

The Calendar: Remember These Days

Most businesses remember these dates. We should too. So here is the official RDK "They Told Us It Was Ready" calendar — and we're not starting it in February. We're starting it in 1998, because this isn't the first coaster they've built while we were already strapped in. One wall. One calendar. Four coasters. Every day an OEM assured us, every day the track shifted, and every day still ahead where the ride could lurch again. Clip it. Save it. When somebody quotes you a 2027 truck, pull it out.

Look at the 2026 stretch of that calendar as one picture. Between February and June, every OEM told us the engines were ready. In July, the regulator quietly handed out relief valves, and the biggest engine maker in the vocational world re-phased its launch by up to a year. Both things cannot be fully true at once. Either the engines were ready, or the industry just negotiated itself a longer runway because they weren't. You know which one my gut says.

Rewind the Tape: 25 Years on This Same Coaster

Now, before anybody accuses me of fearing something new, let's be honest about something: this is not our first ride. Stand at 2025 and look back 25 years, and you'll see we've been strapped into this exact coaster at least three times before — same chain lift, same cheerful loudspeaker, same missing track. That's why the calendar above starts in 1998 instead of February. Scroll back up and read the top half of that wall again — the names change. The ride doesn't.

Look at the pattern across 25 years, because it repeats like a chorus: a new standard is announced → the OEMs assure everyone they're ready → a giant pre-buy empties the order boards → the first-year engines struggle → the early buyers pay the tuition → and three to five years later the technology finally matures. 2002 did it. 2007 did it — and took Caterpillar's on-highway business with it. 2010 did it — and nearly took Navistar. There is no version of this history where the first riders got the smooth ride.

And the rhyme that should really get your attention: the nonconformance penalty — the exact mechanism that let non-compliant engines onto the road in 2002 and kept Navistar's struggling MaxxForce engines selling until a court shut it down — is the same mechanism EPA just proposed bringing back for 2027. We're not guessing how that story goes. We've already read the ending once.

Be Prepared: What to Do With This

Everything I told you in May stands — the July news just underlined it in red ink:

If you need trucks in the next 24 months, lock in proven current-emissions builds now. The pre-buy stampede is real, slots are vanishing, and proven reliability sets the price. Your 2025 and 2026 trucks are appreciating assets in a world where nobody has a mile of data on the replacements.

If you're a large fleet with a long horizon, watch two dates: the EPA final rule (comments close August 29) and the moment a 2027 engine lands in a real customer fleet on real routes. Not a trade-show ride-along. A garbage truck, on a route, in the summer, in Florida. When that happens, we'll all learn something. Until then, the only test data being generated is being generated by whoever buys first.

If you run refuse specifically: the X10 is your future diesel, and its full production is Q3 2027. The Mack LR's 2027 plan is unpublished. The Peterbilt 520's 2027 plan is unpublished. Natural gas (L9N/X15N) remains the one powertrain in this whole story with actual years of proven refuse service behind it. Plan accordingly.

And to be fair to the OEMs one more time: phasing launches, softening warranties, keeping current engines available through the transition — these are all rational, even responsible moves. But rational and responsible is not the same thing as ready, and you deserve to know the difference before you sign.

The Bottom Line

The coaster is leaving the station January 1, 2027, whether the far turn is finished or not. The OEMs are waving from the platform — not because they're villains, but because they're survivors. EPA just padded the seats. And that voice on your shoulder is still whispering, sweet as cotton candy:

At RDK, we're strapped into this ride with you — same market, same stakes, same missing track. We watch it every single week — every OEM announcement, every EPA docket entry, every real street sighting — and the moment a 2027 engine actually shows up working a route, you'll hear it from us, with photos.

Until then: keep your harness tight, keep your proven trucks running, and ask hard questions before you sign for anything with a 2027 sticker on it — no matter whose sign is over the door. Being prepared costs you nothing. Being unprepared has a 25-year track record.

Sources

This letter is the opinion and commentary of the author, Richard Kemner, and is provided for general information only. It is not legal, financial, tax, or regulatory advice, and it is not a purchasing recommendation for any specific vehicle, engine, or manufacturer. All dates, specifications, production schedules, regulatory provisions, and program details are compiled from the public sources linked throughout and are believed accurate as of July 27, 2026. OEM launch plans and EPA rulemakings change — frequently, as this letter demonstrates — so verify all details with the manufacturer, your dealer, and the official EPA docket before making any purchasing decision. The EPA proposal discussed here is exactly that: a proposal, not a final rule. All company names, engine names, and trademarks referenced belong to their respective owners. RDK Truck Sales is not affiliated with, sponsored by, or endorsed by any engine or truck manufacturer named in this letter. The roller coaster is a metaphor; no actual amusement rides were harmed in the making of this blog.