Retrofitting diesel to Euro 6: What other options are there?

Anyone who still has an old diesel vehicle is confronted with more and more problems - whether driving bans, high vehicle tax or environmental zones. Things are getting tight for older diesels. The possibility of retrofitting a diesel seems easy to implement - in practice, unfortunately, this is no longer the case. Many retrofitters no longer offer retrofit kits. More in this article.

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Emission standards: Why retrofit diesel

The latest emission standard is Euro 6e. It has been mandatory for newly type-approved passenger car models since September 2023. All first registrations since September 1, 2024 must therefore meet the 6e standard. But this is only the first stage of the Euro 6e standard – the second stage has been mandatory for newly type-approved passenger car models since January 2025 and for new registrations from January 2026. Here, the emissions strategy used must be displayed during vehicle inspections.

Stage three is then associated with an adjustment of the utility factors and will come into force for new registrations from January 2028. When you see all this, it becomes clear that a Euro 5 diesel certainly no longer meets the requirements for environmental and emission protection.

 

Retrofitting diesel: Too little demand – offers have been discontinued

Diesel vehicles are having an increasingly difficult time. The diesel scandal has severely damaged the image of the engine, and among hybrids, the diesel hybrids, which are actually quite fuel-efficient, are a rarity. The new Euro 7 emission standard is already being discussed, but some old diesels have not even been converted to Euro 6.

Since 2019, the Federal Motor Transport Authority has approved retrofit SCR catalytic converters to Euro 6, but in the meantime all retrofit companies have discontinued their offer for passenger cars (as of January 2025). Demand was too low, and the business was no longer profitable enough for the companies.

 

Retrofit kits for motorhomes and vans still available

The aftermarket for passenger cars has not been worthwhile, but motorhomes and vans are still being retrofitted according to the current status - albeit with limited supply.

• HJS: Focus on retrofitting craftsmen's vehicles
• S.K. Handels GmbH: Retrofitting vans and motorhomes

This is how you could retrofit your old diesel so far

Here is a brief overview of the companies and options available in the past to retrofit a diesel vehicle:

• SCR systems for Euro 5 diesels
• S. K. Handels GmbH has offered an SCR system in cooperation with the company HJS Emission Technology
• Retrofit system from Oberland Mangold was NeoPlus
• Diesel retrofitting with systems from dr pley by bosal for selected Volvo and Mercedes models is no longer available

 

Retrofitting Euro 6 – these were the possibilities in detail

For Euro 5 diesels, there is the option of having an additional exhaust gas purification technology, the so-called SCR catalytic converter, retrofitted. This is a hardware retrofit. The government actually expected car manufacturers to pay for the costs of retrofitting. However, it has been shown that many diesel drivers are left with part of the costs. Volvo and BMW, for example, refuse to financially accommodate customers when retrofitting diesel with SCR systems.

Anyone who owns an older Mercedes or VW can receive up to 3,000 euros from the car manufacturers for approved retrofits from third-party suppliers. But as you can see, since some manufacturers refuse to subsidize, providers of such SCR systems are gradually withdrawing. In view of the rather moderate reputation of the diesel engine and the questionable economic efficiency in connection with the Corona pandemic, the question arises anyway as to whether buying a diesel vehicle is still worthwhile at all. Synthetic fuels currently under development are intended to contribute to solving the problem of pollution. But don't worry: When the combustion engine ban comes in 2035, only new registrations will be affected by the zero emissions limit.

Since the introduction of the Euro 6 standard, diesel vehicles have also had to fill up with AdBlue in order to be able to comply with the limit values. This is a liquid urea mixture that, in combination with an SCR catalytic converter, reduces the emission of nitrogen oxides. Otherwise, particulate filter systems are like other parts in cars: they are wearing parts. A diesel particulate filter must be cleaned or freed at financial expense, as they become clogged with increasing use.

Ob ein Nachrüsten älterer Modelle für das Befahren der Münchner Umweltzone möglich sein wird, wird sich zeigen. Die Stuttgarter Umweltzone hat noch höhere Regelungen.

Nachrüstung von der HJS Emission Technology und der S. K. Handels GmbH

Der Coronakrise sind schon einige Hersteller wie Twintec Baumot zum Opfer gefallen – dafür tun sich neue Anbieter von Katalysator-Systemen hervor. So arbeitet die S. K. Handels GmbH, ein Autohaus mit integrierter Werkstatt und Lackiererei, mit dem Katalysatorhersteller HJS zusammen, um SCR-Lösungen für nachrüstbare Dieselfahrzeuge anzubieten. Auf der firmeneigenen Webseite heißt es, der Anbieter könne zur Zeit Wohnmobile, den Mercedes Sprinter, den VW Caddy sowie den Fiat Ducato auf Euro 6 nachrüsten – also hauptsächlich Kleintransporter und Nutzfahrzeuge.

As part of the exhaust gas aftertreatment by the system offered, the nitrogen oxides produced by fuel combustion are to be converted into water vapor and nitrogen by the catalytic converter. With the addition of AdBlue, exhaust gas purification is achieved. It advertises a reduction in emissions of harmful nitrogen oxides of up to 90 percent.

NeoPlus from Oberland Mangold GmbH

Another option for hardware retrofitting comes from the company Oberland Mangold. The so-called NeoPlus solution reduces the emission of harmful particles in the exhaust gas and is used in vehicle models of the VW Group that were already equipped with an SCR system ex works, but which turned out to be not powerful enough.

Diesel passenger cars with conversion options include the VW Sharan 2.0 TDI, the Seat Alhambra 2.0 TDI and Audi Q5 2.0 TDI quattro automatic. In addition, Oberland Mangold offers the so-called particle catalytic converter, an effective particulate filter system that is used in cars from the manufacturers Audi, Citroen, Peugeot, Volkswagen, Fiat, Ford, Mercedes, Nissan, Renault, Seat and Skoda.

Euro 5 diesel conversion kits from dr pley by bosal

Another SCR solution is the kits from the manufacturer dr pley by bosal. Its SCR systems are also not suitable for a wide range of models – instead, the company is concentrating on providing conversion hardware for the Euro 5 Volvo models XC60, XC70, S60, V60 and V70 as well as the Euro 5 Mercedes models C180 CDI to C250 CDI, E200 CDI to E250 CDI and GLK200 CDI to GLK250 CDI.

The diesel retrofit should take about 3 hours in the workshop. Anyone who owns one of the Mercedes models mentioned above can apply to the car manufacturer and receive up to 3,000 euros back for the retrofit.