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K&N 33-2181 High-Flow Air Filters – Mercedes M272 / M113 V6 & V8 | R350, R500 (Set of 2)
K&N 33-2181 High-Flow Air Filters – Mercedes M272 / M113 V6 & V8 | R350, R500 (Set of 2)
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The K&N 33-2181 is a pair of high-flow, washable panel air filters for the Mercedes R-Class W251 — R350 and R500. This listing includes both filters, because these models use two filter housings and a complete change needs both. Oiled cotton gauze media, made in the United States, drops straight into the factory housings in about ten minutes with no tuning and no modification.
What You Get
| Part Number | K&N 33-2181 |
| Quantity Included | 2 filters (left and right) — one complete vehicle set |
| Filter Media | Oiled cotton gauze, pre-oiled |
| Tune Required | No |
| Install | Drop-in, 5–10 minutes, Torx driver required |
| Reusable | Yes — washable and re-oilable |
| Made In | United States |
| Ships | Within 2 business days |
Cold Air Intakes Aren't Pulling Cold Air
Ironically, "cold air intakes" use open cone filters, exposing them to hot air from the engine bay. Hot air is less dense, so the engine makes less power, and rising IATs push the ECU toward pulling timing. Worst on a hot day when you are actually driving hard.
The factory Mercedes airbox already channels cold air from the outside. Sealed, ducted to the grille. The paper panel inside is the only real restriction, and that is what these performance air filters replace.
Fitment — R-Class W251
| Model | Chassis | Years |
|---|---|---|
| R350 | W251 | 2006–2012 |
| R500 | W251 | 2006–2007 |
Install & Maintenance
Undo the Torx screws on each airbox lid, lift the lid, swap the filter, and put it all back together. No cutting, no wiring, no tuning.
Wash with a cotton-gauze filter cleaner, rinsing from the clean side outward. Air dry at room temperature — no compressed air or heat — then re-oil lightly. Over-oiling is what contaminates a MAF sensor.
Warranty, Shipping & Returns
- Warranty: K&N "No-Hassle" Lifetime Limited Warranty against defects in materials and workmanship.
- Shipping: Ships within 2 business days.
- Returns: 30-day returns on unused items in original packaging.
Questions
How many filters does my car need?
Two. These models use two filter housings, one per bank. This listing ships both, so you are not hunting for a second panel after the box arrives.
Do I need a tune to run these?
No. These are direct replacements for the factory panels and work on a completely stock car. A tune is where the real power is, but it is not a requirement for fitting these.
Will the filter oil damage my MAF sensor?
Not when the filters are oiled correctly. They ship pre-oiled at the right level and need nothing before install. MAF problems come from over-oiling after a cleaning — apply lightly, let it wick in, and do not saturate. If you would rather avoid oil entirely, a dry synthetic filter is the alternative.
Is a cold air intake better than this?
On these models, no. The factory box is already sealed and ducted to outside air, so the paper panel is the restriction rather than the box. An open cone gains a little peak flow and gives up intake temperature, which is the wrong trade. A full intake kit earns its place once you are chasing airflow beyond what the factory box supports.
How often do they need cleaning?
K&N publishes a service interval of 50,000 miles under normal street driving. Clean them sooner if they are visibly loaded — dusty roads and construction traffic shorten that considerably.
Do these fit the factory airbox without modification?
Yes. They are OEM-shape panel filters. Nothing is cut, drilled, relocated or removed, and the factory heat shielding stays exactly as it is.
