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Description
Killer B Motorsport Air Oil Separator 02-07 Subaru Impreza WRX & STi / 04-08 FXTAfter years of being asked to develop a Killer B Motorsport Air Oil Separator, we are proud to announce we have released the GD Air Oil Separator. This is a product weve been asked to develop for many years, and in that time there has been a lot of research, engineering, simulations, development, testing (and repeat), with several Subaru engines and build types. This has been going on over many seasons, exposing to environmental extremes, and driving
After years of being asked to develop a Killer B Motorsport Air/Oil Separator, we are proud to announce we have released the GD Air/Oil Separator. This is a product we’ve been asked to develop for many years, and in that time there has been a lot of research, engineering, simulations, development, testing (and repeat), with several Subaru engines and build types. This has been going on over many seasons, exposing to environmental extremes, and driving conditions (daily driving, auto-X, drag racing, dyno testing, etc.), as well as on stock engines and exceeding 700whp.The goal of this product is simple. To function as its Air/Oil Separator description implies: the removal of oil, in liquid or vapor form, from the vented crankcase gasses. Simple in premise, but function wise there’s a bit more to it. Varying oil droplet sizes, with differing pressure and velocity conditions. Different engines with varying venting characteristics or a street car vs a track or performance elevated engine. The variable list goes on, making acceptable function and performance a difficult challenge.
Performance must be spot on, but the effect on the engine’s operation must be unchanged at the least, or improved ad best. We prefer the later. This is accomplished by using a design that has no restrictions; media or baffles, to reduce the flow potential of the crankcase and head vents. Under positive boost conditions it will produce vacuum in the crankcase. The benefit of this is improved evacuation of crankcase gasses and the many other benefits that can be had with crankcase vacuum; improved ring seal, reduced oil consumption and improved power potential.
The Killer B Motorsport Air/Oil Separator functions with a vacuum source only, the turbo inlet. This provides the vacuum source for the crankcase. It is in no way effected by the turbo size, in fact a larger turbo that draws more air will improved separator function, compensating for increased venting requirements seen at improved performance levels. While small OEM turbochargers produce crankcase vacuum under boost, larger turbochargers produce even more. Drain back design assures that any oil accumulation ends up where it needs to be, in the oil pan, providing a consistent oil supply to the engine. Six stainless steel bolts on the top, make it quick and easy for inspection and cleaning. It is not heated and we see no reason to add unnecessary cooling/heating (weight, complexity, increased install time, and increase probability of something leaking) and this simple engineered form functions just fine without it. The Killer B Motorsport Air/Oil Separator should meet and exceeds your expectations of how an Air/Oil Separator should work and function on a Subaru engine. Not only that, it will display some of the best eye candy fabrication available. The Killer B Motorsport Air/Oil Separator is a product that you the enthusiasts, have been waiting years for.
Shipping Notes
- Free Standard Shipping on $100+ Orders to the USA.
- Except Preorder products are shipped in 48 hours.
- Delivery to the USA:
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Exchange/Return Notes
- We offer a 30-day return/exchange service after receiving.
- Final sale items are not eligible for returns or exchanges.
- To process your return/exchange, please contact us at [email protected]
- Please click here for more details>>> Return & Exchange Policy
4.6 ★★★★★
Based on 933 reviews
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Product Reviews
★★★★★ 5
Great cordless frother
Color: Black
This milk frother has been a great addition to my daily coffee routine. It comes with multiple useful accessories, which make it versatile for different drinks and easy to clean afterward. The motor is impressively powerful, producing rich, creamy foam in seconds. Exactly what you’d expect from a quality electric frother, which typically delivers fast, consistent results with minimal effort.
I also really appreciate the convenient charging base, which keeps everything organized and ready to go without dealing with loose cords. What stood out most, though, was the customer service. I had a minor issue with the buttons, and they quickly sent a replacement with no hassle. Overall, a reliable, well-designed product backed by excellent support.
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Reviewed in the United States on April 30, 2026
★★★★★ 5
Best frother for many reasons
Color: Black
I spent a long time searching for the right frother because of how much I would be using it. I make coffees, teas and protein shakes daily. I needed something more high powered than normal. Ive had others that just dont get the job done and/or dont last. (the 3 others I tried were all free gifts with a purchase of coffees or teas online. So now that i was paying for one, i wanted something better with all the good features)
Its has 3 attachments for every possible use (if u dont know what the hook one is for, its great for protein drinks or any heavier powders u need to mix) but honestly all 3 attachments work for heavier powders due to the stronger motor. U can use it for cooking as well. The stand charger is super convenient and space saving. Multiple power/level settings. Definitely a quality item but with a bargain price. The cherry on top is the customer service. They're great! responsive and very helpful. Im definitely happy with this purchase and will now be looking into see what other products they have to offer. 🙂
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Reviewed in the United States on March 29, 2026
★★★★★ 5
Excellent customer service and good product.
Color: Black
Really like this frother a lot, with the attachments. Great price and works well. That being said, it suddenly stopped working after a few months, to my dismay. However, upon reaching out to the company, they replaced it very quickly. So I do recommend it!
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Reviewed in the United States on April 25, 2026
★★★★★ 4
Great frother, dumb charger
Color: Black
Works well. I got this to replace my battery powered milk frother from IKEA. I use it to make a protein shake every day. I just take a 16oz glass, fill it halfway with milk, add a scoop of protein powder, and mix it with the frother, using a combo of low and medium power, but realistically, low is all you need for that purpose. Been using it everyday for the past almost month since I got it, haven't had to recharge it and it's still working great.
The only reason I'm giving 4 stars instead of 5 is because the charger is micro USB. Not using USB-C in 2025 is honestly just insulting. Change that and you have a 5-star product.
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Reviewed in the United States on August 12, 2025
★★★★★ 5
Best frother I have bought
Color: Black, Color: Black
Easy to use
Rechargeable
3 speeds for different nixing
Has a rechargeable stand that helps make it stand up straight
And didn’t forget to register the unit for the warranties
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Reviewed in the United States on April 28, 2026