BMW's S55 Oil Scavenging System - The Ultimate N55 Performance Upgrade

BMW has always done a good job with its oil scavenging system while retaining the wet sump setup on BMW M cars, and the S55 is no different. While the S55 engine shares a lot of its basic engine block architecture with the non-M N55 engine, it uses an entirely different oiling system which does a phenomenal job of ensuring a healthy supply of oil to the bearings under all sorts of operating conditions. This system is good enough that it is utilized in the factory-built F22 M235iR/M240iR and the F82 M4 GT4 race cars. Aftermarket companies make baffles for the N55 pan, but they can’t match BMW’s OE engineering. Luckily, the shared architecture means your N55 can benefit from S55 parts.

BMW S55 Oil Scavenging System

Although the N55 and S55 have sensitive oiling systems, M Division's improvements are shockingly simple yet effective. For starters, the S55 engine utilizes a large main sump towards the rear of the engine. That part of the sump is where the oil drains, and the engine will pull oil from. To keep up with the M3 and M4 chassis requirements, BMW included an integrated baffle plate to keep as much oil as possible around the oil pick-up tube under extreme lateral forces. The N55 doesn’t have the integrated baffle and suffers because of that. Owners have found out the hard way that an aftermarket baffle is essential for their engines to survive repeated hard cornering on a race track. 

The S55 also differs from the N55 as it has two oil pumps. The main oil pump, responsible for supplying oil to the engine, is driven off the crankshaft via chains but pulls oil from the central part of the sump. Working in tandem is the scavenge oil pump (driven by the main oil pump). It’s specifically tasked with ensuring there’s never a drop in oil pressure and pulls oil from four locations:

• The front left of the oil pan
• The front right of the oil pan
• The front turbocharger oil return (cylinders 1-3)
• The rear turbocharger oil return (cylinders 4-6)

The oil pulled from these four sources continually feeds into the main sump through the oil return flow pipe. The pipe forces the returning oil into a part of the baffle called the swirl pot, which drains the oil into the main sump even under the highest lateral or longitudinal forces. It’s a relatively simple system but incredibly effective when done right. 

This system is so effective that BMW retained it for use on the F82 M4 GT4 and F22 M225iR/M240iR. Those race cars will typically use slick tires, allowing higher sustained lateral loads. Even in this extreme situation, oil starvation is not a problem. BMW claims that this system guarantees a consistent and constant oil supply up to a longitudinal acceleration of .61g down to -1.2g. Furthermore, this system ensures a constant oil supply of up to 1.2g of lateral acceleration (hard cornering, for example).  

BMW N55 To S55 Oil Pump Retrofit

As mentioned earlier, this system is interchangeable with the N55 engine due to the similar engine block architecture. For those who track their rear-wheel drive, N55-powered BMW, you can add on this oiling system as a plug-and-play factory upgrade. Adding a baffle to N55 oil pans certainly helps, but the S55 system completely resolves any possibility of oil starvation without running a dry sump system.

You will need more than a handful of parts to retrofit the S55 oil scavenge system onto any N55 in an RWD BMW 135i, 335i, or 435i. With that said, the total cost of the retrofit is much less than the asking price for a used long block and doesn’t require a degree in rocket science to install. Everything required can be bought as Genuine BMW parts, though we recommend grabbing OE or OEM parts if you aren’t concerned about having a BMW logo on parts you won’t see. 

Parts Required To Retrofit The S55 Oiling System To An N55 Engine

• S55 Oil Pan
• Main oil pump
• Oil deflector (suction pipe)
• Oil pump sprocket (re-use your existing chain)
• Secondary oil pump (scavenge pump)
• Secondary oil pump shaft
• Oil pan gasket
• Oil pan screws
• A handful of other bolts and gaskets

Those are all of the parts you’ll need to swap over to the much more durable S55 oiling system. If that seems daunting, we wouldn’t blame you, as part numbers and bolt counts can be tricky to find. But fear not; FCP Euro is always here to help. Instead of dredging through forums and Facebook posts in hopes that you have a complete parts list, you can simply buy yourself the FCP Euro BMW S55 Oil Pan and Oil Pump retrofit kit. Using a mix of Genuine, OE, and Aftermarket parts, our retrofit kit contains every single nut, bolt, washer, and gasket you’ll need to guarantee your N55’s oiling system at the race track.

Shop Our BMW S55 Oil Pan & Oil Pump Retrofit Kit

Last thing; consider grabbing some CSF cooling components as well to essentially bulletproof your engine for hours of track time to come.

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Written by :

Gareth Foley

Gareth is the BMW Make Level Marketer for FCP Euro and has been with the company since 2012. Gareth's BMW obsession started with a hand me down E39 528i when he was 17. From this car he learned how to do his own repair work while also learning more about BMW. When Gareth was at CCSU studying Marketing he had the opportunity to go to SEMA with the college car club. This is where he developed his love of the automotive industry. Since joining FCP in 2012 Gareth has sought out to develop one of the broadest and most accurate BMW replacement parts catalog. he can be reached at gareth1@fcpeuro.com