Ultracool M8 Naked Oil Cooler - `2017-2023

UltraCool M8 Naked Oil Cooler for 2017-2023 Harley Milwaukee-Eight engines, a side-mount auxiliary cooler that works with the factory cooler to prevent overheating in traffic and city riding. Features a dual-fan aluminum heat exchanger with automatic thermal control that keeps oil in the optimal 200–230°F range.

Features

• Side-mount on down tube, no cover (naked design)
• Dual-pass aluminum heat exchanger with turbulators
• Sealed IP68 waterproof dual fans produce 220 CFM airflow
• Automatic thermal switch activates fans at 210°F, shuts off at 185°F
• Plug-and-play wiring harness with relay and waterproof connectors
• Black nylon-coated stainless steel braided oil lines with AN6 fittings
• LED indicator light shows when fans are operating

Specifications

• Brand: UltraCool
• Manufacturer Part #: SMT8-3
• Length: 11 in
• Width: 9 in
• Height: 6 in
• Weight: 8 lbs

Fitment

Fits 2017-2023 Harley-Davidson FLH Milwaukee-Eight (M8) frames with oil-cooled or air/oil-cooled engines. Works alongside the factory oil cooler to manage full-engine oil circulation.

Frequently Asked Questions

Why do I need this if my M8 already has a stock oil cooler?

Stock M8 coolers struggle in traffic and city riding. This auxiliary cooler cools ALL engine oil, giving M8 performance comparable to a fully liquid-cooled motor in hot conditions.

What temperature range does this maintain?

The automatic thermal switch activates fans at 210°F and shuts them off at 185°F, keeping oil in the optimal 200–230°F window.

Is installation difficult?

No — it's plug-and-play. The wiring harness connects to the battery under the seat, and oil lines use included AN6 fittings with the provided wrench.

Will this fit my air/oil-cooled M8?

Yes — this kit works on both oil-cooled and air/oil-cooled FLH M8 frames from 2017-current.

What's included in the box?

The cooler assembly with dual fans, thermal switch, plug-and-play harness with relay, braided oil lines, LED indicator light, fitting wrench, and installation instructions.