As with any other cars I've ever owned.
K&N and AEM have always been my favorite a/f.
With my 2013 SL550 the only choices I seem to have are either K&N or BMC.
I searched on the internet and I've seen mixed bag reviews.
Any opinion or feedbacks are welcomed.

 

Stick with stock or at least a dry filter. Mercedes are highly temperamental.

 

This. In the 40+ cars I’ve owned I’ve not really found aftermarket filters to be beneficial. In all of my German cars I’ve just run stock air filters, unless a CAI was involved, which was rare. To each their own, though.

 

Don't do it. Oiled filters are know to foul MAF sensors.

 

All good advice. I know it may not seem sexy, but paper element air filters do not exist to remove horsepower (and btw, they don't). They're air filters. They keep abrasive grit from entering your engine and reducing its healthy lifespan. At least, paper ones do. Aftermarket filters are designed to sell you something, not to improve your engine's life in any way. K&N "filters", for example, are basically oily rags with holes in them. They can (and do) claim whatever they want for HP gains, but if they're truly passing more air than similar-sized paper elements, then they're also passing more dirt. There's no free lunch here. I think M-B engineers probably know how to design proper engine air filters, and they chose paper.

The comment about oiled filters fouling MAF sensors is no joke, either. I had this happen to me back in the day, with my '88 Thunderbird Turbo Coupe. I fell for the promotional BS and installed a new, factory-oiled K&N in the car's stock filter housing, and in short order it started running poorly. Guess who needed a new MAF sensor. Another aspect to oiled elements: if you don't drive the car very often, the element oil tends to gel over time, and actually begins restricting airflow! I had this happen as well...kind of counter to the "filter's" mission statement, no? Do your car and yourself a favor...stick with stock paper filter elements. If you worry about them clogging, or whatever, just change them more often. JMO, but based on personal experience.

Another un-sexy fact: almost every car, for the last many decades, has come from its factory already equipped with genuine cold air induction. That's free HP that no factory has passed up. I've rarely seen an aftermarket "CAI" that was not actually a hot air induction. They virtually never route their intake air from a true cold air source as thoroughly as the factory setups do...