Harley® Oil Cooler & Motorcycle Oil Cooler Systems Welcome to a new generation of Harley Davidson oil coolers. The latest innovation for your Harley-Davidson® and V-twin motorcycles. Whether you’re traveling the back roads of America, stuck in a traffic jam, or just cruising the city streets, oil temperature is a constant threat to the rider and engine safety. We help this issue by keeping your engine oil flow running cooler with the best motorcycle parts in the USA, while adding comfort and safety to your ride. Welcome to the UltraCool Reefer® Oil Cooling System.