The key structural difference from CE — for most machinery, CE marking can be a manufacturer's own declaration, reviewed by an outside body only if the manufacturer chooses to go further, as covered in our CE certification article. EPA's Certificate of Conformity works differently: it is issued directly by the federal agency after reviewing the manufacturer's emissions test data for that specific engine family, not simply declared by the manufacturer on its own authority.

Which standard actually applies to the XN13's engine

Our XN13 is powered by a Kubota D722 engine rated at 10.2 kW (14 hp). Under EPA's power-based classification system, that places it in the smallest regulated nonroad diesel category, engines rated under 19 kW (under 25 hp). Industry sourcing on this exact engine confirms the Kubota D722 is EPA Tier 4 Final certified, the current and most stringent US standard for nonroad diesel engines, in effect since 2015 for the power classes used in most mini excavators.

What Tier 4 Final actually limits

Tier 4 Final sets specific numeric limits on particulate matter, nitrogen oxides, and hydrocarbons, tightened substantially from earlier tiers. Technical documentation on the standard cites limits such as 0.02 g/hp-hr for particulate matter on most engine sizes and roughly 0.40 g/hp-hr for nitrogen oxides on mid-size nonroad engines, values that effectively require modern emissions control technology to achieve, compared with older, unregulated or lightly regulated engines.

Why this specific engine class does not need DEF

This is a detail worth knowing before you buy, because it affects day-to-day operating cost. Industry guidance on Tier 4 engines is specific: diesel exhaust fluid (DEF, also called urea) is required only on engines that use selective catalytic reduction (SCR) technology to meet NOx limits, and that is generally engines above roughly 75 hp. At 14 hp, the XN13's engine sits well below that threshold. In practice, this means no DEF tank to monitor, no urea to buy and top up, and no risk of a DEF-related engine derate if the fluid runs low, a genuine ongoing cost and maintenance item on larger Tier 4 Final machines that simply does not apply here.

Side by side

General comparison — not a claim about every competitor's engine

	EPA certification	CE certification (most machinery)
Who issues it	The EPA itself, after reviewing test data	Often the manufacturer's own declaration
Governing law	Clean Air Act, 40 CFR Part 1039	EU Machinery Directive 2006/42/EC
What it specifically governs	Engine exhaust emissions	Broader machinery health and safety requirements
Verifiable document	EPA Certificate of Conformity	EU Declaration of Conformity

What to ask for, and how to verify it

Ask for the engine's EPA emission control label information and, where available, the Certificate of Conformity reference for that specific engine family. A supplier who can show you this is describing a real, government-reviewed compliance status, not a marketing phrase. Be cautious of any supplier offering a "new" machine with an older, Tier 3 or earlier engine for US sale: industry compliance guidance notes these older engines generally cannot be newly manufactured or imported for sale in the US, which makes an EPA-compliant engine the only legitimate option for a new machine regardless of price.

What this does not mean

EPA certification addresses engine exhaust emissions specifically. It does not certify the machine's general build quality, structural safety, or mechanical durability, those are separate questions covered by other parts of a buying decision. It also does not mean every Tier 4 Final engine behaves identically: power class, aftertreatment technology, and maintenance requirements still vary across engines even within the same tier.

Questions to ask before you buy

1. Can you provide the engine's EPA emission control label details and Certificate of Conformity reference?

2. What power class is the engine rated in, and does that class require DEF?

3. Is the specific engine family currently in production, or an older engine being offered on a "new" machine?

Ask us directly through our inquiry form for the XN13's emissions documentation. You can review the full specification on the XN13 product page.

Frequently asked questions

Feature availability varies by model, configuration, and market; confirm current certification documentation directly with Rhinoceros before purchase. Regulatory information is drawn from published EPA documentation and industry compliance guidance, current as of October 2026.