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VLF credit for Diesel Particulate Filter Retrofits in Germany

by Rafael Seidl

After years of wrangling between federal and regional governments, the German cabinet is now ready to submit a bill to parliament detailing a system of vehicle license fee (VLF) credits and penalties for diesel particulate filter (DPF) retrofits.

The upper chamber will have to start deliberating the bill by 15 December in order for it to become law in time for the 1 April 2007 target date. The measure is independent of the current Euro 4 emissions regulation level and only applies to vehicles registered in Germany.

Specifically, any light-duty diesel vehicle initially registered on or before 31 December 2006 will enjoy a one-time credit of €330 (US$439) on their vehicle license fee on the day its owner proves to the authorities that a DPF was retrofitted between 1 January 2006 and 31 December 31 2009. For qualifying retrofits executed before the law goes into effect, the credit becomes effective on the day that it does.

Note that there are two types of qualifying filters: wall-flow filters, which are ~98% effective and reduce PM emissions below the level of the future Euro 5 regulations today. This type requires periodic regeneration and hence, an engine control unit featuring software to execute that. Given the high thermal stresses that can occur in the monolith while burning off the soot, the software must be fine-tuned to each engine and exhaust design. Quite a few current-generation vehicle models are already shipping with wall-flow filters as standard equipment.

For many other models, it is now an available factory-installed option that prescient buyers have already shelled out for. For these—and only these—models, a wall-flow filter can also be retrofitted, but at €600 the price tag is substantially higher than the factory-installed option.

The other type of DPF is called flow-through and is only 30-50% effective. However, it requires no regeneration cycles and is therefore also suitable for legacy vehicles. For example, the PM emissions of a vehicle originally certified at Euro 1 will be lowered to roughly the Euro 2 level.

Aftermarket suppliers already offer suitable devices for some but far from all makes and models, priced at €550-700 installed depending on vehicle model. Unfortunately, in many older underbody designs, there is simply no room to install any DPF.

The price differential is why the tax credit applies only to retrofits and not to vehicles shipped with factory-installed DPFs. To fund it, the proposed law will impose an annual penalty of €1.20 per 100 cubic centimeters of engine displacement through Dec 31, 2011 on the following two classes of diesel vehicles:

  1. Those initially registered on or before December 31, 2006 but still without a filter of either type; and

  2. New vehicles that do not meet the future Euro 5 limit of 5 mg/km particulate emissions. Presumably, "new" in this context refers to an initial registration date after Jan 1, 2007.

Since 1 January 2005, Austria has offered a one-time €300 credit for new vehicle registrations featuring a DPF. This is funded by a commensurate penalty for those that do not. However, financial support for DPF retrofits is currently only offered in three regions and several cities.

Note that the EU also requires all local governments to take remedial action if their ambient PM level exceeds a threshold level for more than 35 days in a given year.

Respected mostly in the breach last winter, there is now a proposal in Germany to require all owners of light-duty diesel vehicles to obtain a official decal advertising which level of the Euro emissions regulations they were certified/retrofitted to with respect to PM. On days with poor air quality, diesel vehicles below the minimum certification level defined for that day would not be permitted to operate at all in that municipality. It’s not immediately clear if or when this additional red tape will go into effect and, how it will mesh with the DPF retrofit law. (Earlier post.)

According to the Austrian automobile association OeAMTC (Unsere Luft, ISBN 3-900235-84-8, in German), only 6.6% of PM2.5 emissions in 2005 could be traced back to LDV diesels and another 8.4% to HDVs. The rest came from space heating, industry, power plants, off-road diesels and agriculture. However, these values reflect averages across the country. In city centers, on-road diesels presumably play a bigger role.


fyi CO2

Good measure to clean up some of the antiquated diesel ICEs in the Bundesrepublik - does this only apply to particular branded filters, or will there be a gray market filter to boot?

Rafael Seidl


the article didn't say but I strongly suspect that only DPFs on an official list will qualify for the credit. If there is such a list, a particular DPF model would have to be certified by someone, e.g. the German TUeV. I also suspect the labor has to be executed by a certified mechanic to qualify.

The average age of the LDV fleet in Germany is about 8 years now. That means there are indeed quite a few early 1990s diesels (Euro 1 & 2) still on the road. Owners of such newtimers may be reluctant to invest in them, preferring to pay the penalty for a couple of years before trading up to a used Euro 4 car with a wall-flöw DPF. Note that Euro 4 only came into force in Oct 2005.

The bulk of the fleet consists of Euro 3-certified. For these, a flow-through retrofit may make sense as they tend to still have quite a few years of useful life left in them. This is even more true of Euro 4 cars, of course, if only to maintain resale value.


I like the way things are done in Europe. Desirable outcomes are encouraged by subsidy, paid for by penalties on undesirable activities. In America, we subsidize undesirable activities (e.g. tax deduction worth $20K on purchase of a Hummer used in "business") and pay for them by borrowing.

Rafael Seidl

George -

fiscal responsibility becomes an essential discipline for politicians when the executive branch is elected indirectly by parliament, i.e. there is (usually) reliable majority for a four-year term. It does take some time to cobble together formal coalitions (Austria is undergoing this right now). However, once they are in place, bills do get passed - including the less palatable ones, like this DPF law. It´s not like people who own a car that for technical reasons cannot be retrofitted at all are jumping for joy about it. However, there is also no confusion about who is accountable for the direction of the country at any given time.

In presidential democracies (USA, France, others), a common configuration is that the executive and the legislative branches are in different hands, because that is how voters try to retain checks and balances in day-to-day practice. The past 6 years in the US were something of an anomaly in that regard. Cohabitation, as the French call it, is inefficient in that it is based on separate election results rather than a negotiated formal coalition agreement spanning a broad range of contentious topics. The result tends to be horsetrading aka vote buying among legislators, which puts severe upward pressure on the overall budget. In the long run, this is viable only if foreigners are prepared to help finance it (e.g., by propping up the US dollar or, by paying French farmers ludicrous subsidies).


Can anyone advise on availability in the US of the flow-through type filters for US light trucks? I have two late model diesels (pre-2007) that I would potentially be interested in installing these filters on, assuming the cost isn't too high and there isn't a significant penalty in mileage or power.

Rafael Seidl

Zach -

you may want to contact e.g. Emitec USA directly to find out if they have a device for your truck make, model and year. They should also be able to tell you where you could buy it and get it installed in your area.

3250 University Drive, Suite 100
Auburn Hills, MI 48326-2390

Tel.: 001-248-276-6430
Fax: 001-248-276-6431

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