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Fit a filter

Fitting an approved filter to your exhaust could reduce your vehicle’s emissions enough to meet the Low Emission Zone (LEZ) emissions standards.
If you do choose this option, be aware that ordering the filter, and getting it fitted and certified takes at least three months, so you need to act as early as possible and pay a daily charge if driving within the zone in the meantime.

Step 1 – Choose and order a filter

It’s important to fit an approved filter, as this is the only way to get the certificate to prove that your vehicle meets LEZ emissions standards.

Approved suppliers and their contact details can be found in the following document:

Approved equipment lists can be found in the following documents:

Accredited equipment manufacturers can advise you on approved filters for your particular vehicle. We recommend you contact several filter manufacturers and get a minimum of three quotes.

When requesting a filter quotation it’s important that you provide (via email or phone):

  • Vehicle make
  • Vehicle model
  • Body type/style (eg motor home/caravan, light 4×4 utility, van)
  • Drive cycle/vehicle use (eg urban/inner city, suburban, motorway/long distance) and percentage of time spent in each type of driving
  • Gross Vehicle Weight (tonnes or kg)
  • Year of manufacture
  • Engine size/displacement (litres)
  • Engine power (bhp/kW)

Approximate cost of buying and fitting a filter

  • The cost of buying and fitting abatement equipment will vary depending on the age, type and usage patterns of your vehicle
  • Buying a filter will cost between £1,800 and £3,500 for most vans, minibuses and other specialist vehicles and between £3,500 and £7,000 for HGVs, buses and coaches
  • Fitting costs are often included in the purchase price, and are generally between £200 and £500 for vans, minibuses and other specialist vehicles and between £300 and £500 for HGVs, buses and coaches
  • For large vehicles or those which have been specially modified, costs may be higher. It may prove cheaper to upgrade to a newer model which meets the standards, rather than retrofit an older vehicle

Maintenance costs

  • Most filters will need to be serviced once a year, depending on how many miles are travelled
  • Some filters can be self-serviced by the vehicle operator, but most require a full service by a suitably trained mechanic. This will cost around £100-£200 for vans, minibuses and other specialist vehicles, and around £150-£350 for HGVs, buses and coaches

We recommend that you seek a range of quotes before making a purchase.

We are not responsible for suppliers failing to respond or for the quotations received.

The table below includes details of accredited suppliers and the vehicles they have filters for:

Lorries, buses, coaches and heavy specialist vehiclesLarger vans, minibuses and specialist diesel vehicles
Ab Proventia
0845 5194624
 Yes No
Astra Vehicle Technologies
+44 (0) 151 348 5777
 Yes Yes
01908 821103
 Yes Yes
Dinex Exhausts
+44 (0) 192 584 9849
 Yes Yes
Emicon Systems
0203 289 2892
 Yes Yes
+44 (0) 142 781 0088
 Yes Yes
Green Urban
+44 (0) 1744 883166
 Yes No
HJS Emission Technology
+44 (0) 1344 360 173
 Yes Yes
Pirelli Eco Technology
07513 743 365
 Yes Yes
01427 787122
 Yes Yes

Step 2 – Get it fitted

The supplier of your filter should be able to recommend an approved fitter, who will fit the filter into your exhaust system (often replacing the exhaust silencer).

Make sure you keep all the documentation for the engine and filter, as you’ll need to provide this to the Driver and Vehicle Standards Agency (DVSA), formerly VOSA, to get a certificate for your filter.

DVSA are the government agency that carries out annual tests on all lorries, buses and coaches, and licences MOT garages. It also tests filters and issues all certificates showing that vehicles meet the LEZ standards.

Step 3 – Get it certified

Once your filter has been fitted, it’ll need to be tested so you can get your Reduced Pollution Certificate (RPC) or Low Emission Certificate (LEC) to prove your vehicle meets the LEZ emissions standards. You can get a LEC for all types of vehicle, but RPCs are only issued to certain lorries, buses and coaches.

You can either have your filter tested by an Authorised Examiner or at a DVSA test station.

Option 1: Book and take a test with DVSA

Each DVSA test costs £32. To find your nearest centre and book your test, call 0300 123 9000.

DVSA will examine your vehicle to confirm that the filter fitted is approved, and will carry out a smoke test to confirm that it’s fitted and functioning correctly (the smoke test doesn’t measure the particulate matter emissions of your vehicle). Once the test is successfully completed, DVSA will issue either a LEC or RPC and submit this to us automatically.

It may take up to 10 days for our database to be updated, so in the meantime, you’ll need to pay the daily charge if you’re driving in the LEZ.

Find out about specialist tests for lorries on the DVSA website

Option 2: Take a test on site with an Authorised Examiner

You may find that the fitter of your filter is a DVSA Authorised Examiner (AE), which means they will be able to test your vehicle for you (and you won’t need to book a separate test with DVSA). A fee of £32 will be charged for the test. If not, your filter supplier may be able to recommend a mobile AE who can carry out the test for you at your premises.

Once the test is successfully completed, the AE will submit documentation to DVSA, which will conduct a quality check on the documentation received.

If everything is in order, DVSA will issue either a LEC or RPC to the vehicle owner by post and will notify us that the certificate has been issued.

It may take up to 10 days for our database to be updated, so in the meantime, you’ll need to pay the daily charge if you’re driving within the LEZ.

Remember to re-test every year

RPCs and LECs are normally valid for 12 months, after which you’ll need to get your vehicle re-tested, or pay the daily charge if you’re driving within the LEZ.

If you have a lorry, bus or coach, your first RPC or LEC will be valid until your next annual vehicle inspection at DVSA to allow you to schedule the test at the same time.

If you have a larger van or minibus, you will need to get your vehicle re-tested at a DVSA test centre or at any one of the participating non-DVSA LEC testing sites.

Find a list of sites where vehicles can be taken for an LEC test on the GOV.UK website

Please contact the site directly. This test is separate to your normal annual MOT. Please note that most AEs can only test filters the year they are fitted.

When presenting your vehicle at a DVSA test station or to an AE you must produce the previous original LEC issued to the vehicle.

Please check the current fees for a LEC test by DVSA and for certificates issued following an examination by an AE. Any additional fees incurred for tests carried out at an approved AE site should be discussed with the approved AE directly.

It is very important to:

  • Follow the filter manufacturer’s maintenance schedule so that the filter doesn’t block
  • Heed any warning lights or loss of vehicle performance and contact the filter installer if this occurs. It may mean that there is a build-up of soot in the filter that has not burned off. The trapped soot has a similar chemical composition to coal and needs to burn off at high temperatures. If the filter becomes overly laden with soot it can lead to increased back pressure, which can cause the trapped soot to combust and release heat. This can cause the filter to fail rapidly and means the vehicle would no longer pass the annual test at DVSA

Case studies

Lorries, buses coaches & heavy specialist vehicles

Larger vans, minibuses & specialist diesel vehicles

Tips for Changing a Diesel Engine’s Air and Fuel Filters-How do you fit a diesel fuel filter?

The air filter setup on most diesel engines is the same as that of gasoline-powered vehicles, with the filter located inside the cold air collector box located under your hood. Most diesel has two fuel filters: one “primary” between the tank and engine; this cleans any dirt in it before getting to transfer pump; second, which gives final cleaning near injectors called secondary.


Changing your fuel filter is a simple task that you can do on some diesel cars like unscrewing the old one and moistening it with gas before screwing in the new cartridge.

Both fuel filters are usually easy to change, and your owner’s manual should show you how to do this job. On some diesel, such as those where they have replaceable cartridges for their main filter (you just remove the old one and pop in a new cartridge), this process might be even simpler than changing an oil or air filter.

However, there also exist certain models of car which require more work; these use what’s called ‘servo-controlled filtering systems – replacing them requires special tools because each has its own unique design

To change the fuel filter in a diesel vehicle, you need to pump air bubbles out of the system and prime it. This process is called bleeding because if not done correctly, exhaust could come through your vents or make its way into your cabin.

To bleed this system yourself without damaging anything requires an air-bleed screw which can be found on most newer models along with a manual primer pump for added support.

To start the car, you first need to prime it with some gas. So pull out your trusty primer and pump until you hear hissing noises that indicate all of the air has escaped. Once this happens tighten up your screw on top of the primer before putting back into place.


When your diesel car needs a new air filter, you must ensure to turn off the engine and open up all of the doors before accessing that area. A hairpiece could slip into this hole while it’s still hot or wet from driving – leading to serious damage in an instant!

The input is: “You have to take one big precaution when you change the air filter on a diesel: Always shut off the engine first.”



When the weather starts to get cold, it’s best for you to change your diesel fuel filters. Dirty or clogged filters can make starting and idling difficult which could result in stalling when driving so be sure not to let this happen!

There are two types of filters: one that is located on the line between where we put our phone number and the engine (the primary fuel filter) while another less common secondary type is found near engines instead. So don’t delay if you’re planning a road trip soon before winter sets in again because changing both sorts should help ensure all goes smoothly with any start-ups along longer routes ahead especially since these rides may take us further than ever before!



Fuel filters for your diesel vehicle should be replaced every 10,000 miles to ensure optimal performance of the engine. A typical schedule may mention a normal or severe replacement cycle which you will probably opt for as most drivers take short trips under various hot and cold weather conditions that require more rigorous care.

When you’re ready to replace your fuel filters, reference the owner’s manual. This way you’ll have all of the necessary information on hand including size details when making a trip to an automotive supply store. Here are some tips for replacing diesel fuel filters:

The first fuel filter will be on the fuel line and should be located underneath your vehicle. Place an oil drain pan directly under where you think it is, then places a tool such as an Allen wrench or hex key into one of the holes in order to remove what looks like a cap from its housing. Once removed allow for all gas to flow out before replacing with a new filter by securing the plug again.

Remove the first fuel filter by loosening it with a wrench and socket. Extracting this one is easier than removing the primary filter, as all you need to do is pry off its O-ring using a flathead screwdriver. Afterward, put on your new O-ring that comes standard in every replacement part from now on before popping the cap back into place for easy removal next time around!

The primary fuel filter is the first one most people replace. Using a wrench and socket, loosen it before removing it with your fingers to ensure you do not scratch anything. Remove using both hands until free of its housing then set aside for later disposal after purchasing new rings or o-rings depending on what type was in place previously at an auto parts store.

The secondary fuel filter is located near the engine. To replace it, grab an oil drain pan and move underneath where you will be working so that any excess fluid can fall into the container rather than your boots or garage floor! The first step off with removing all hoses connected to this part before getting started. Following steps 1 through 3 you should have finished replacing your secondary fuel filter successfully

When it is time to replace your fuel filters and diesel, don’t throw the old ones out like trash. There are multiple options around where you can recycle these items depending on what’s available in your area – check with city services or ask at a dealership for advice. Completely clean up any messes made during this process before updating maintenance records so that when its next scheduled date comes, you know how long ago it was completed.

In order to keep your diesel-powered vehicle running smoothly, you need to make sure that the fuel filters are changed at regular intervals. DEFdeletekits has a wide selection of replacement parts and can answer any questions about replacing them correctly. provides you with a choice of diesel fuel filters. To know more about your vehicle’s filter, have a chat session with our expert!


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