The KN 303 is a spin-on oil filter made by Knecht, a German filtration company owned by Mahle

The Knecht KN 303 is a cylindrical oil filter that screws onto the engine block. It traps dirt, metal particles, and debris from engine oil before that oil circulates back through the engine. Knecht manufactures filters for European vehicles, and the KN 303 appears in service manuals and parts catalogs for certain Volkswagen, Audi, Skoda, and Seat models, primarily from the 1980s through early 2000s.

If you are replacing an oil filter during an oil change, the KN 303 is the part you remove and throw away. A new filter of the same type screws back on in its place. The filter itself does not repair anything or improve performance — it straightforward keeps the oil cleaner so the engine lasts longer.

Key Takeaways

  • The KN 303 is a spin-on filter that screws directly onto the engine block and traps particles from circulating oil.
  • This filter fits specific Volkswagen, Audi, Skoda, and Seat models, mainly from the 1980s through early 2000s, so you must confirm your vehicle's year and model before ordering.
  • You replace the KN 303 during every oil change, typically every 5,000 to 10,000 miles depending on your vehicle and oil type.
  • The filter costs between $8 and $20 depending on the retailer, and you can install it yourself with basic tools if you have done an oil change before.

Which vehicles use the KN 303

The KN 303 appears in parts lists for Volkswagen Golf, Jetta, and Rabbit models from the 1980s and 1990s, as well as some Audi and Skoda vehicles from the same era. Knecht filters were original equipment on many European cars, so if you own one of these vehicles and the service manual calls for a KN 303, that is the correct part.

The safest way to confirm is to check your owner's manual or service record. If you do not have the manual, you can look up your vehicle's year, make, and model on an auto parts website — most will show you which filter fits. Do not assume the KN 303 fits your car based on the model name alone, because the same model name was used across many years and engine sizes, and not all of them took the same filter.

How to find the right replacement

When you are ready to replace the filter, you need three pieces of information: your vehicle's year, the engine size (usually listed in liters, like 1.6L or 2.0L), and the model name. With those details, you can search for "KN 303 replacement" or "oil filter for [your car]" on any major auto parts retailer's website.

If the KN 303 is no longer in stock — which is common for filters designed for vehicles 20 or 30 years old — the parts site will usually suggest a modern equivalent that fits the same thread size and has the same filtration capacity. Mahle, which owns Knecht, makes many of these replacements under the Mahle brand name. A modern filter will work just as well as the original KN 303 would have.

Cost and where to buy

A new KN 303 filter, when available, typically costs between $8 and $20 depending on the retailer and whether you are buying online or in a physical store. Shipping can add another $5 to $10 if you order online, so buying locally may be cheaper for a single filter.

Auto parts chains like AutoZone, O'Reilly, and NAPA carry Knecht filters or equivalents, as do online retailers like Amazon and RockAuto. European specialty shops that focus on Volkswagen or Audi parts often stock Knecht filters or have them in their catalog. If the exact KN 303 is out of stock, ask the retailer for a cross-reference — they can tell you which modern filter has the same specifications.

Installing the filter yourself

If you change your own oil, replacing the filter takes about five minutes. The filter screws onto a threaded port on the engine block, usually on the side or top. You unscrew the old filter by hand (or with a filter wrench if it is too tight), wipe the threaded port clean with a rag, and screw the new filter on until it is snug.

The only tool you might need is a filter wrench — a metal band or cup that grips the filter so you can turn it without your hands slipping. If the filter is not too tight, you can remove it by hand. When you install the new filter, screw it on by hand until the rubber gasket on top touches the engine block, then turn it another three-quarters of a turn. Do not use a wrench to tighten it, because over-tightening can damage the gasket and cause leaks.

If you have never changed an oil filter before, watch a video for your specific vehicle model first. The location of the filter port varies, and you want to know where to find it and what tools you will need before you start.

When to replace the KN 303

You replace the oil filter every time you change the oil. Most vehicles need an oil change every 5,000 to 10,000 miles, though some newer cars can go longer. Check your owner's manual for the interval your vehicle recommends.

If you do not drive often, replace the filter at least once a year, even if you have not reached the mileage interval. Oil breaks down over time, and a filter that has been in the engine for a year collects moisture and particles that can damage the engine if left in place.

What happens if you use the wrong filter

Using a filter with the wrong thread size will not screw on at all, so you will know when ready that something is wrong. Using a filter that is too small or has lower filtration capacity than the original can let more particles through, which may shorten engine life over time, but you will not notice a problem right away.

The safest approach is to confirm the correct filter before you buy. If you are unsure, ask the parts retailer or a mechanic — they can look up your vehicle and tell you which filter is correct. Spending five minutes on a phone call is faster than buying the wrong part and having to return it.

Frequently Asked Questions

Can I use a different brand of filter instead of the KN 303?

Yes. As long as the replacement filter has the same thread size and filtration rating, it will work. Mahle, Bosch, Mann, and other brands make filters that fit the same engine port. The KN 303 is straightforward the original Knecht part number — modern equivalents from other manufacturers perform the same job.

How do I know if my filter is clogged?

A clogged filter usually triggers an oil pressure warning light on the dashboard. If the light comes on and you have not changed the oil recently, the filter may be the problem. The safest response is to change the oil and filter right away. Driving with a clogged filter can damage the engine because oil cannot circulate properly.

What do I do with the old filter after I remove it?

Most auto parts stores will take used oil filters for recycling at no charge. Some require you to buy a new filter from them first. You can also take it to a hazardous waste collection site in your area. Do not throw it in the trash — the oil inside is toxic and can contaminate soil and water.

Is the KN 303 still made today?

Knecht stopped making filters for older vehicles as those cars left the road. If you cannot find a KN 303 in stock, a modern Mahle or equivalent filter with the same specifications will work. Parts retailers can cross-reference the old part number to find what is currently available for your vehicle.