W221 Wiper Blades: The Right Size, Brand, and Why It Matters

If you own a Mercedes W221, replacing your wiper blades is one of the easiest maintenance tasks on the car — assuming you get the right size. The W221 uses 27-inch blades on both sides, and this is not a case where you can just grab a pair of blades off a rack and call it done. The intermittent wiper function on the W221 is sensitive to blade weight, and using mismatched sizes creates a problem that is annoying to diagnose if you don’t know what you’re looking for.

I’ve dealt with this firsthand on my own W221 and have seen it come up repeatedly. Some owners opt for two differently-sized blades causing the rain-sensing wipers to behave erratically, skipping, hesitating, or running at the wrong speed for the conditions. The fix is always the same: two matching 27-inch blades.

The Right Wiper Blade for Your W221

The blade I recommend, and the one that was fitted to your car from the factory, is the Bosch AeroTwin 27-inch set. Bosch is the OEM supplier for Mercedes-Benz, meaning these are the same blades that went on the car when it was built. You can buy them under the Mercedes part number and pay a significant premium, or buy the identical blade from Bosch directly. There is no functional difference.

Bosch AeroTwin 27″ Wiper Blade Set

The AeroTwin is a beam-style blade rather than a traditional bracketed wiper. That matters on the W221 because the beam design applies consistent pressure across the full length of the blade, which improves contact on the curved windshield. It also has no external frame to collect ice or debris, which is relevant if you’re running this car through a winter.

One thing worth knowing: these blades last about a year under normal use. With regular cleaning — running a damp cloth along the rubber edge when you wash the car — they hold up longer. Dirty blades wear faster and streak more, so it’s a simple habit worth building.

Why Both Blades Must Be the Same Size

A lot of aftermarket wiper sets are sold as a 28-inch driver side and 26-inch passenger side. On most cars, using slightly different sizes is fine — the blades still clear the glass adequately and there’s no functional issue. The W221 is not most cars.

The W221’s intermittent wiper system uses the rain sensor in the windshield to determine wiper speed, but it also uses the resistance and timing of the wiper sweep to calibrate itself. When the two blades are different weights — which a 28-inch and 26-inch blade will always be, even from the same manufacturer — the system detects an imbalance in the sweep pattern. The result is intermittent wipers that hesitate, stutter, or run at an inconsistent speed. It can look like a rain sensor fault or a wiper motor issue, and it’s neither. It’s just the wrong blades.

This is why 27/27 is the correct fitment, not 28/26.

Part Numbers

Both the Bosch and Mercedes part numbers refer to the same blade. The only difference is the packaging and the price. If a shop quotes you the Mercedes part number, you can cross-reference it to the Bosch number and source it yourself for less.

Check Your Wiper Arms Before Installing New Blades

New blades on damaged wiper arms is a waste of money. It takes an extra 60 seconds to check the arms before you swap the blades, and it’s worth doing.

Lift both wiper arms away from the windshield and hold them up. Be careful not to drop the arm onto your windshield, but they should stay in position on their own. If an arm drops back down rather than holding its angle, the spring tension inside the arm pivot is worn out. A tired arm won’t apply enough pressure to the glass, and even a brand new blade will skip, smear, or leave streaks because of it. Wiper arm replacement is a separate job but a straightforward one, and the arms themselves are inexpensive.

While you have the arms lifted, look at the pivot where the arm attaches to the wiper linkage. Corrosion at the splined connection is common on older W221s, especially in northern climates. If the connection looks corroded, a spray of penetrating oil at this point is worth doing before you start removing the blades — it prevents the blade attachment clip from snapping off the arm if it’s stuck.

How to Install Wiper Blades on a W221 S-Class

The W221 uses a standard hook arm attachment, so the AeroTwin blades snap on without any tools. The whole job takes under two minutes once you’ve done it once.

That’s it. No tools needed, under two minutes per blade if the clips aren’t corroded. If the attachment clip on an old blade is stuck and won’t release, don’t force it — work some penetrating spray into the connection and give it a moment before trying again.

More W221 Maintenance and Guides

If you found this useful, our complete W221 S-Class guide covers everything about the platform — models, engines, production figures, and more. For anyone considering a W221 purchase, our individual model guides for the S600, S63 AMG, and S65 AMG each include a buyer’s section with common ownership considerations.