From model year 2027, every new heavy-duty diesel engine sold in the United States has to meet a far tighter limit on nitrogen oxides (NOx). Canada’s rules follow the US standards, so the trucks sold here take the same step. If you’re pricing a truck this year, the question is simple to ask and harder to answer: buy before the change, or after it?
This guide sets out where the rule stands as of October 5, 2026, what actually changes on a model year 2027 truck, and how to weigh a new truck against a used one with your own numbers. The used trucks on our yard list their model year and engine, so you can check each one against what follows.
Reviewed every month
The rule is still moving: EPA proposed changes in July 2026 and hasn’t published a final rule. We check the Federal Register and EPA’s rule page every month until it does, and the “Last reviewed” date above shows when we last did.
Where the rule stands, as of October 5, 2026
In January 2023 the US Environmental Protection Agency (EPA) issued its final rule on heavy-duty engines and vehicles. From model year 2027 it sets tougher standards for NOx, particulate matter, hydrocarbons and carbon monoxide, adds new test cycles, and lengthens the emission warranty and the “useful life” an engine must stay clean for.2 The NOx limit on the main test cycles drops to 35 mg/hp·hr, from the 200 mg/hp·hr that applies through model year 2026: a cut of more than 80 percent.31
35mg/hp·hr
NOx limit over the FTP and SET test cycles, model year 2027 and later
50mg/hp·hr
NOx limit over the new low-load cycle
650,000miles
useful life of a heavy heavy-duty engine from model year 2027 (11 years or 32,000 hours)
On March 12, 2025, EPA said it would reevaluate the 2023 rule. On July 14, 2026 it published a proposal that keeps the model year 2027 NOx standards (“which the EPA is not reopening”) but changes the warranty, the useful life and how engines respond to diesel exhaust fluid (DEF) problems.1 Public hearings were held July 29 and 30, and comments closed August 29, 2026.6 When we checked on October 5, 2026, no final rule had been published, so the 2023 rule is still the one on the books.3
EPA 2027 milestones
EPA publishes the final rule
Tougher standards and longer warranties and useful lives for model year 2027 and later heavy-duty engines (88 FR 4296).2
EPA says it will reevaluate the rule
Truck and engine makers, suppliers, fleets and dealers raise the cost of the longer warranty and useful life.1
EPA takes up DEF complaints
The Administrator says EPA will look at whether engine derates are still needed to make sure DEF is used.1
US greenhouse gas standards repealed
A separate rule ends all US greenhouse gas standards for heavy-duty vehicles and engines.7
EPA proposes amendments
NOx standards kept; warranty and useful life eased; penalties offered for late engines; derates replaced by warnings (91 FR 43154).1
Comments close
Next comes a final rule. No date for it had been announced when we checked.6
- Today, Oct 7, 2026
Model year 2027 engines arrive
EPA says most makers expect a full lineup of compliant engines; a few engine families may not be ready for a January 2027 start.1
Longer useful lives, under the proposal
If the proposal is finalized as written, the longer useful lives start here instead of in model year 2027.1
Dates from the Federal Register (88 FR 4296; 91 FR 7686; 91 FR 43154) and EPA’s rule page, checked October 5, 2026. Model years don’t always start on January 1.
What changes on a model year 2027 truck
The rule is written for engines, sorted by the kind of truck they’re meant for. Most highway tractors run “heavy heavy-duty” engines: EPA’s class for engines designed for several rebuilds, normally in tractors and trucks over 33,000 lb GVWR. City tractors and smaller dump and refuse trucks normally use “medium heavy-duty” engines, for vehicles of 19,501 to 33,000 lb.5
A heavy heavy-duty diesel engine before and after model year 2027
| Model year 2026 and earlier | Model year 2027, the 2023 rule | Model year 2027, the July 2026 proposal | |
|---|---|---|---|
| NOx limit, FTP and SET cycles | 200 mg/hp·hr | 35 mg/hp·hr | 35 mg/hp·hr (not reopened) |
| NOx limit, low-load cycle | No low-load cycle | 50 mg/hp·hr | 50 mg/hp·hr (not reopened) |
| Emission warranty | 100,000 miles or 5 years | 450,000 miles, 10 years or 22,000 hours | 100,000 miles or 5 years (kept from 2026) |
| Useful life | 435,000 miles, 10 years or 22,000 hours | 650,000 miles, 11 years or 32,000 hours | 435,000 miles until model year 2029; 650,000 from 2030 |
| When DEF runs low or the SCR is tampered with | Engine derates and speed limits | Derates, written into the rule | Warnings you can see or hear; no derate |
| Engines not ready in time | — | — | May sell with a penalty, up to 200 mg/hp·hr NOx |
40 CFR 1036.104 (Tables 1 and 4) and 1036.120 (Table 1), up to date as of October 1, 2026; the proposal, 91 FR 43154 (sections III, IV and V). Warranty and useful life: whichever comes first. Checked October 5, 2026.
Warranty and useful life: the part most likely to change
Under the 2023 rule, the minimum emission warranty on a heavy heavy-duty engine jumps from 100,000 miles or 5 years to 450,000 miles, 10 years or 22,000 hours, whichever comes first.4 The useful life, the distance over which the engine has to keep meeting the standards, goes from 435,000 miles to 650,000.3
EPA now proposes to keep the model year 2026 warranty periods for 2027 and later engines, and to start the longer useful lives in model year 2030. It counts the longer warranty as the biggest single cost in the 2023 rule, and estimates the change would save buyers up to US$6,000 a diesel vehicle in warranty costs, savings it expects makers to pass on.1 If you’re waiting for a 2027 truck because of the long warranty, that reason may not survive the final rule.
DEF derates
Most diesel trucks have used selective catalytic reduction (SCR) and DEF to cut NOx since model year 2010. When DEF runs out, is poor quality or the system is tampered with, engines have been made to lose power or speed, which EPA calls an inducement. The proposal would replace those derates with warnings you can see or hear on newly built engines, and EPA says it is considering guidance for engines already on the road.1 Until a final rule says otherwise, treat the trucks you look at as working the way they were built.
Engines that aren’t ready on time
EPA says most truck and engine makers have told it they’ll have a full lineup ready for model year 2027, but a few diesel engine families may not be finished in time. The proposal would let makers of medium and heavy heavy-duty diesel engines sell those for a while if they pay a nonconformance penalty, with NOx no higher than 200 mg/hp·hr, the model year 2026 standard.1 If you order a 2027, ask which standard its engine is certified to.
Canada and BC: which rules apply here
Canada’s On-Road Vehicle and Engine Emission Regulations require a diesel heavy-duty engine to meet the US standards for its model year, and they read the US Code of Federal Regulations “as amended from time to time”. An engine covered by an EPA certificate may meet that certificate’s standards instead.8 In February 2025 the federal government said that, with EPA’s tougher heavy-duty standards, the regulations would need amendments to stay aligned, and that it intended to develop them within the year.9 When we checked, the regulations had last been amended on October 3, 2022.8
Greenhouse gases are a separate story. The US repealed all its greenhouse gas standards for heavy-duty vehicles and engines, effective April 20, 2026.7 Canada’s Heavy-duty Vehicle and Engine Greenhouse Gas Emission Regulations are its own, and were still in force when we checked.10
At the port, the model year comes first
If the truck will haul containers in and out of the Port of Vancouver terminals, check the port’s rules before you look at price. Since January 1, 2025, a truck added to, replacing one in or returning to a Truck Licensing System fleet has to be a 2018 model year or newer, with compliant or factory-installed emissions components.11
New or used before EPA 2027?
There’s no single right answer. It depends on when the truck has to start earning, what it will do and how long you’ll keep it. Here’s what each choice gets you, on the facts above.
A used truck now
- The rule doesn’t touch it. The 2027 standards are for new engines; a used truck stays certified to the standards of its own model year.3
- It works today. It can earn now, at a used price, on SCR and DEF hardware that has been in trucks since model year 2010.1
- Its condition is the risk. Kilometres, maintenance and the aftertreatment’s health matter more than the rule. Read the spec sheet and get it inspected.
A new truck built before model year 2027
- New, on today’s rules. A model year 2026 heavy heavy-duty engine carries the maker’s emission warranty of at least 100,000 miles or 5 years.4
- The price is higher than used, and EPA itself notes makers’, fleets’ and dealers’ concerns about the cost of new trucks under the 2023 rule.1
Waiting for a model year 2027
- The cleanest engines, to 35 mg/hp·hr of NOx.3
- New hardware, with little road time. In EPA’s words, “no company has real-world data on MY 2027 production hardware over the range of applications in which these engines may be used.”1
- An open question on warranty. 450,000 miles under the 2023 rule, or 100,000 under the proposal: it depends on the final rule.41
Decision helper
New or used before EPA 2027?
Three quick questions. Worked out in your browser; nothing is saved or sent.
If you answer
- Now, or within a few months and Yes, port drayage
Start here
A 2018 or newer truck, new or used
For port work, the model year decides whether the truck can join a Truck Licensing System fleet at all. Check the port’s current rules with its TLS team, then compare trucks that pass.
If you answer
- Now, or within a few months and No, other work and Keeping the price down
Leaning
A used truck, inspected properly
It can start earning now at a used price. Put the money you save into a proper inspection and a close look at the aftertreatment and its records.
If you answer
- Now, or within a few months and No, other work and A new truck with the maker’s warranty
Leaning
A new or late-model truck built before 2027
You get the maker’s warranty without waiting for model year 2027 engines. Ask for the engine’s model year and check it on the emission label.
If you answer
- I can wait into 2027 or later and A lot: it’s why I’d wait
Leaning
Wait for the final rule, then decide
If the long warranty is your reason for a 2027, it hangs on EPA’s final rule. We update this guide every month until it’s out.
If you answer
- I can wait into 2027 or later and Not much: I budget for repairs myself
Leaning
Decide on the numbers, not the rule
New or used, run both through the worksheet below with real quotes, and buy the one that costs you less over the years you’ll keep it.
A starting point, not advice: your work, your quotes and the final rule decide.
Run your own numbers
Put a new truck and a used one side by side over the years you’d keep either. Use real quotes and your own fuel and repair records; we don’t fill in any prices.
Worksheet: your numbers
New against used, over the years you’ll keep it
Your numbers stay in your browser.
Your result
New minus used, over the years you keep it
—
New truck: what it costs you
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Used truck: what it costs you
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New truck, per km
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Used truck, per km
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Fill in your numbers to see the result.
Your figures only. Leaves out financing, tax, insurance, licensing and downtime; add any you know to the repair lines. Not financial advice.
Financing through our sister company Blue Capital Equipment Finance Ltd., an affiliated broker, at the same Surrey yard. Blue Capital explains how equipment loans and leases work, and the truck payment calculator turns a price into a monthly estimate.
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Before you buy, new or used
Five steps before you sign
Start with the work
Port drayage, regional or long haul, vocational: the work sets the model year you need, the spec and how long you’ll keep the truck.
Check the engine’s model year
It’s the engine’s model year the standards follow. Find it on the engine’s emission label and the listing, and make sure they agree.
Read the records
Ask for the maintenance history and an ECM report, and look hard at the DEF, SCR and particulate filter.
Price both ways
Get real quotes for a new and a used truck and run them through the worksheet above.
Recheck the rule before you sign
If the warranty or the derates swing your decision, check whether EPA’s final rule is out.
We’d rather you make the right call slowly than the wrong call fast. From our family to yours.
FAQ
EPA 2027 questions
Has the EPA 2027 rule been delayed?
Not the NOx limits. As of October 5, 2026, the 2023 rule still sets them for model year 2027, and EPA’s July 2026 proposal says it isn’t reopening them. The proposal would keep the model year 2026 emission warranty and start the longer useful lives in model year 2030, but it isn’t final yet.
Does EPA 2027 apply to used trucks?
No. The standards are for new engines from model year 2027. A truck built earlier stays certified to the standards of its own model year.
Does Canada follow the EPA 2027 standards?
Canada’s On-Road Vehicle and Engine Emission Regulations require heavy-duty diesel engines to meet the US standards for their model year, read as the US rules are amended, and accept an engine’s EPA certificate. In February 2025 the federal government said they would need amendments to stay aligned with EPA’s tougher standards, and that it intended to propose them.
Will DEF derates go away?
EPA has proposed replacing them with visible or audible warnings on newly built engines and says it is considering guidance for engines already on the road. Nothing changes until a final rule or guidance is published.
What is a nonconformance penalty?
A payment that would let an engine maker keep selling an engine that isn’t yet clean enough for the new standard, for a time. EPA proposes making it available for medium and heavy heavy-duty diesel engines from model year 2027, with NOx no higher than 200 mg/hp·hr.
How often do you update this guide?
Every month until EPA publishes a final rule, and whenever EPA or Canada changes something. The “Last reviewed” date at the top shows our latest check.
