"In this Special Series about the Mechanical Restoration, I document the repairs, the replacement parts and the mechanical upgrades to the E46 M3. 

In this entry, I inspect the OEM oil cooler, discuss options and unbox the S54 Performance Oil Cooler by Radtec. I document its unique features and installation."
-Matt

More revs, more cooling. 

With the upcoming S54-EVO high duration camshaft program, upgrading the oil cooling was an obvious while you're in there as part of the mechanical restoration of the Phoenix. 

The core fundamental of the Sxx-EVO program resides on increasing rev limiters to make sure of the higher duration camshafts to pair with shorter gears. Increasing power and revs will increasing cooling needs. The end goal is to have a +/- 8,600 RPM S54 with over 400 PS at the crank. 

Although I do not have immediate plans to track the car, Quebec's Summers get extremely humid and can see +40C (104F) at nearly 100% humidity. As my original oil cooler was 20 years old, and had seen 190,000 km, replacing it was in the cards.

The original cooler was good. 

BMW M designed a 2 component oil cooler: the cooler itself and a plastic sleeve with air ducts.  The Genuine BMW oil cooler was made by Modine to BMW M's specifications. They are a global OE supplier of cooling solutions to various industries. 

As is most cost with OEM components, they are a compromise that optimizes for cost and technical specifications.

It was well built, proving its reliability over 2 decades without any leaks. 

The cooling capacity ultimately degrades over time due to expected wear and tear. They can be cleaned to restore part of its efficiency, but some is most often lost. 

The original plastic sleeve.

The original oil cooler was further designed with plastic sleeve. It has an integrated cowl with ducts leading air onto the cooling fins and away from the air-to-water radiator.

The Genuine BMW sleeve doesn't have a cowl in the traditional sense - it's at the back! The purpose is to optimize air flow of the complete cooling systems and improving cooling efficiencies of the S54.

The sleeve is a unique feature to the E46 M3 when compared with the V8 and V10 cramped engine bays and front fascia. 

The oil cooler sits parallel to the radiator unlike modern turbo M engines that are parallel to the ground. It takes its air from the lower bumper grill area. 

There are a myriad of oil cooler options on the market for the S54 from known brands such as CSF, DO88, Mishimoto and others. 

My selection process had a few variables: 

1. It needed to fit with the original ducted plastic sleeve for the cooler. 
2. It needed to improve cooling performance in some way.  
3. It needed to come from a reputable brand

CSF

The CSF was eliminated as it has documented quality issues and also appears to offer no cooling increase per feedback from track oriented E46 M3 owners.  Having most experience in the V8 and V10 world of cooling, I wasn't surprised as this is also the case for their S65 cooler package.

Mishimoto

Mishimoto's oil cooler is the sucker's choice. Most E46 M3 owners often aren't aware of any other alternative, and Mishimoto is sold by every other shop in the world at prices that riva European made products for one made in China. I don't deal in China parts unless I have to due to market constraints. 

DO88

D088 has been the choice for the V8 owners, and would have been if it hadn't required to eliminate the plastic sleeve. It's an upsized oil cooler that integrates a cowl. The oil capacity, active cooling area and total dimensions are all massively increased. I can source it for your E46 M3 project here. 

Radtec

RadTec is a UK based manufacturer of cooling solutions for OEM automotive manufacturers such as Koenigsegg and has created various aftermarket solutions for BMW M cars. 

I discovered RadTec in 2022 with their S85 performance oil cooler solution. I have put it to use across harsh and changing weather environments as the M5 is my daily. From -40C to +40C, it's proven effective at keeping the S85 in its prime oil cooling range, without suffering from leaks. 

Darren at Radtec informed me they had a few E46 M3 products, including an OE+ replacement oil cooler designed to fit within the plastic sleeve.

I ordered one along with the S85 in 2022 and it sat on the shelf since. 

The cooler is powdercoated in black. A nice aesthetic touch to hide its presence behind the bumper grill. 

By retaining fitment with the original plastic ducted sleeve, the overall shape, surface area and oil capacity is confined to OEM dimensions. 

The improvement is in the core and build quality. The uprated core is more efficient than OEM and is able to better dissipate heat over the original unit. 

Radtec's build quality is second to know. Their aluminum coolers are TIG welded to higher standards than OEM, and the fittings are CNC machined to precisely fit the original oil lines. They can also be machined to fit AN lines. 

We pulled the oil cooler from storage during the Spring '24 round of further mechanical upgrades to the Phoenix. 

During a test fit, the lines bolted in without a fuss. We proceeded with fitting it in the sleeve after completing the installation. 

Plastic has a tendency to shrink over the years. The fit was very snug and needed a proper push. 

This was a simple upgrade that should prove useful as the car gets back on the road in 2024.

It offers a new option for E46 M3 owners that are looking for a smart, quality cooling solution without breaking the bank.

The Radtec S54 oil cooler is available here.