It’s pretty common knowledge that the BMW N54 and N55 Turbocharged I-6 engines run very hot. Considering that turbochargers are exhaust driven, this makes sense- they’re naturally going to be hot and accumulate a lot of heat. This heat generation, coupled with the fact that BMW E82 135i and E9X 335i models have a small radiator, means that under spirited driving conditions (like your favorite canyon), your coolant temperature can exceed 250 degrees – more than 20 degrees above what’s considered “hot” for other cars (230* F). This overheated condition can send your car into “Limp Mode”, making your drive home a whole lot less fun.

Why is this extra 20 degrees so bad? Well for one, engines don’t like excess heat, and that causes wear on components, but more specifically, as the temperature of the motor oil increases, the oil begins to break down and starts losing its viscosity, meaning your oil can’t protect your engine’s internals as well. Lowering the oil’s operating temperature will significantly decrease oil breakdown due to heat, leaving your oil properly viscous and better able to protect the moving parts of your engine that need lubrication.

This "Torture Test" published by Castrol illustrates how quickly running at 260*F oil temp breaks down your oil. This thermal breakdown prevents your oil from properly lubricating your engine.

This “Torture Test” published by Castrol illustrates how quickly running at high oil temperatures breaks down your oil. This thermal breakdown prevents your oil from properly lubricating your engine.

Many early turbo BMW E82, E90, E92 and E93 models did not include an oil cooler from the factory or have one that’s simply too small for the job. In 2006, the 335i did not have an oil cooler – an error BMW quickly recognized, and an oil cooler was added the next year. Unfortunately, this still wasn’t enough as the coolers still are not large enough to offset the heat generated by the turbochargers. So basically, any kind of spirited driving will QUICKLY have your engine operating much hotter than it should be, causing your oil to stop lubricating your engine’s moving parts properly and even overheat. Considering that BMWs are intended to be driven hard, this can make it hard to enjoy the ultimate driving machine.

 So, what can you do to remedy the situation? BMW attempted to fix the problem by adding a small oil cooler to later N54/N55 models – but this still isn’t enough. This is why if you do any of spirited driving at all or just want to extend the life of your motor, you should install an oil cooler large enough to sufficiently cool the oil, keeping your engine running cool and happy.

E92 Jeff MRR GT7 Wheels 18x8.5 18x9.5 225-40-18 255-35-18 CKS Coilovers (9) Fortunately, the engineers over at Evolution Racewerks have developed a solution. Through their experience in racing their using these turbocharged BMW engines in their 135i, their Sport-level Oil Cooler is 9″x8″X2″ (11″x8″x2″ with end tanks), compared to the factory oil cooler which measures a paltry 8.75″x4.75″x1″ – what that translates to 144ci capacity for the ER Oil cooler versus just 41ci for the OEM unit. That’s 350% larger than the factory oil cooler!

Sports Oil Cooler Kit

Simply installing an oil cooler will do wonders for extending the longevity of your turbocharged BMW N54/N55 Engine, and you can further enhance the cooling capacity of the oil cooler by pairing it with the optional shroud that is designed to direct cool air straight into the oil cooler, which are also designed to fit with a variety of different front bumpers for E9X and E82. If you track or enjoy spirited driving in your favorite canyon or mountain pass on a regular basis, you may want to upgrade to the Competition Series Twin Cooler, which as the name suggests, doubles the cores, creating an oil cooler setup with 700% more volume than the OEM unit for maximum cooling capacity.

Competition Oil Cooler Kit


E92 Jeff MRR GT7 Wheels 18x8.5 18x9.5 225-40-18 255-35-18 CKS Coilovers (11)

If you have questions about getting an oil cooler for your E82 or E90, E91, E92 or E93 with an N54 or N55 turbo Inline 6, we invite you to talk to our Modification Experts by calling 714-582-3330 or chat online at

Of course, if you’re local to Southern California, you can bring your Bimmer to our full-service shop here in La Habra, CA. Our expert installers have a lot of experience installing these oil coolers and put the greatest level of care into their installs, ensuring that it’s always done right, the FIRST time.

Story & Original Photos by Nick Gregson
Select Photos Courtesy Evolution Racewerks