Euro 6 for trucks: what the standard requires, DGT label, low-emission zones and Euro 7

In the used truck market, Euro 6 is now the most common standard, yet questions remain: what exactly it requires, what the letters that go with it in adverts mean, which label the DGT (Spain's traffic authority) gives it and what will change with Euro 7. This guide explains it all from the point of view of someone who buys a truck and puts it to work.

A note on naming: for heavy-duty vehicles the standard is written with Roman numerals (Euro VI) and for cars and vans with Arabic numerals (Euro 6). In adverts and in conversation both forms are used for the same thing.

What Euro VI is and when it became mandatory

Euro VI is the European emissions standard for heavy-duty vehicle engines — trucks, tractor units and buses — laid down in Regulation (EC) No 595/2009. It applied to new approved types from 31 December 2012 and has been mandatory for all new heavy-duty vehicles registered in the EU since 31 December 2013.

It replaced Euro V with a clear goal: cutting nitrogen oxides (NOx) and particulates, the two most problematic pollutants from diesel engines. In practice, therefore, a truck first registered new from 2014 onwards is Euro VI, while one from 2013 or earlier may be Euro V or even older: always check the documents rather than going by the year.

Emission limits: Euro V vs Euro VI

Euro VI cuts the nitrogen oxides limit by 80% compared with Euro V and halves the particulate mass limit; it also regulates particle number and ammonia for the first time.

The test cycles are not identical — Euro VI introduced the World Harmonised WHSC and WHTC cycles, which are more representative of real-world use — so the comparison is indicative. In the WHTC transient cycle, the Euro VI NOx limit is 0.46 g/kWh.

What a Euro VI engine has

The standard sets limits, not technologies, but in practice almost all Euro VI engines combine an SCR catalyst with AdBlue, a diesel particulate filter (DPF) and exhaust gas recirculation (EGR). Some manufacturers comply without EGR, relying on a high-efficiency SCR system.

• SCR (selective catalytic reduction) catalyst. Injects AdBlue — a 32.5% urea solution — into the exhaust to convert NOx into nitrogen and water.
• Diesel particulate filter (DPF). Traps soot and burns it off in regenerations: passive ones, while the truck is running at a good pace, or active ones, triggered by the engine.
• Exhaust gas recirculation (EGR). Feeds part of the exhaust gas back into the intake to lower the combustion temperature and, with it, NOx.
• Diesel oxidation catalyst (DOC). Fitted upstream of the filter, it helps the regenerations.
• On-board diagnostics (OBD). Monitors the system and, if it detects that AdBlue is missing or that the system is not working, warns the driver and eventually limits engine performance.

Day to day, this means always keeping AdBlue in the tank and periodic filter regenerations. Short trips and a lot of idling make regenerations harder; a truck used that way needs its filter watched more closely.

Euro VI stages: from A to E

Within Euro VI there are stages identified by letters, from A to E, which were introduced step by step over almost a decade. The basic emission limits do not change between them: what gets stricter is on-board diagnostics (OBD) and in-service conformity testing, which is carried out with portable emissions measurement systems (PEMS) fitted to the truck on the road.

In adverts it is common to see “Euro 6c”, “Euro 6d” or “Euro 6e”, borrowing the passenger-car naming. On a truck, what appears in the type approval is the Euro VI stage.

When buying used, the stage matters less than the actual condition of the aftertreatment system: a well-maintained first-stage Euro VI is usually a better buy than a more recent one whose system has been mistreated.

Euro V and Euro VI day to day

A Euro VI pollutes far less and has access to more zones, but it adds aftertreatment systems that need maintenance and can fail. Most Euro V trucks already had an SCR catalyst with AdBlue (with exceptions, such as some MAN and Scania engines that met the standard with EGR alone); what Euro VI makes universal is the particulate filter and, on most engines, EGR alongside SCR, with more sensors and more diagnostics. A Euro V is mechanically simpler because it has no particulate filter and often no EGR either.

• Consumption. On diesel, the differences depend heavily on the model and the engine generation; on top of that comes AdBlue consumption, which most Euro V trucks already had and every Euro VI needs.
• Maintenance. More sensors and more chemical and electronic components mean more points of failure. Aftertreatment faults are among the most expensive repairs on a modern truck.
• Perceived reliability. A well-maintained Euro V usually has fewer aftertreatment faults than a Euro VI of similar age. Not because Euro VI is badly designed, but because it has more systems.
• Access and resale. Euro VI carries the DGT's C label and has more of a future in low-emission zones, which weighs on resale value.

Which DGT environmental label a truck carries

For heavy-duty vehicles, the DGT label depends on the engine's Euro standard: a Euro VI truck carries the C label (green); a Euro IV or Euro V truck, the B label (yellow); and older ones have no label.

The label is assigned using the data in the DGT's Vehicle Register and can be checked with the registration number on the DGT's online services portal (sede electrónica).

Low-emission zones: what the law says and how it affects you

Spain's Law 7/2021 on Climate Change and Energy Transition requires municipalities with more than 50,000 inhabitants and island territories — as well as those with more than 20,000 inhabitants that exceed pollution limit values — to set up low-emission zones (ZBE, zonas de bajas emisiones). Each city council sets out in a bylaw which labels may enter, in which zones, at what times and on what timetable.

In practice:

• Restrictions are based on the DGT label. Vehicles with no label are the first to be shut out; some bylaws already restrict the B label too in certain zones or at certain times, and the general trend is for the rules to tighten over time.
• Every municipality is different. Many bylaws have their own rules for goods distribution, with loading and unloading hours, permits or grace periods.
• Before you buy, check the bylaws of the municipalities where you work or where your customers are.

Outside Spain, each country has its own system:

• Germany: environmental zones (Umweltzonen), which require the green sticker; for diesel vehicles that means Euro IV or higher.
• France: the Crit'Air sticker; on a diesel truck, Euro VI corresponds to Crit'Air 2 and Euro V to Crit'Air 3.
• Other countries — the Netherlands, Belgium, Italy… — have their own schemes, some of them stricter on trucks. Check them before planning routes.

Euro 7: what changes and when

Euro 7 is governed by Regulation (EU) 2024/1257. For trucks and buses it applies to new approved types from 29 May 2028 and to all new heavy-duty vehicles registered from 29 May 2029. It does not affect trucks that are already registered, which can still be driven and sold.

The main changes:

• A single regulation for cars, vans and heavy-duty vehicles, which until now had separate standards.
• Stricter limits under real driving conditions and over a longer part of the vehicle's life (longer durability requirements).
• Smaller particles: counted from 10 nanometres.
• Brakes and tyres: for the first time, emissions that do not come out of the exhaust are regulated, with their own timetable that starts with cars and vans.

Some technical details for heavy-duty vehicles are being completed through later acts of the European Commission. For anyone buying a used truck, Euro 7 changes nothing straight away: what will drive a truck's value over the coming years is its access to low-emission zones, which depends on its label.

What it all means when buying a used truck

If your work takes you into cities with low-emission zones or your customers require a modern fleet, look for Euro VI. For long-haul work or away from urban areas, a well-maintained Euro V can still make sense if the price makes up for it.

• Urban distribution, or shippers that require a modern fleet: Euro VI.
• Long-haul and international: Euro V is still viable, but check the environmental zones in the countries you pass through.
• Construction and out-of-town routes: Euro V can do the job.
• A horizon of five years or more: Euro VI, because access to cities and resale value count for more and more.

Either way, on a used Euro VI what matters most is the condition of the aftertreatment system. Our guide on what to check before buying a used tractor unit explains how to check it. And if you are looking for a vehicle, you can browse our stock of tractor units and trucks, with the emissions standard shown on each listing.