At the heart of the new system is GM's 2020 Duramax L5P oil cooler. This cooler rejects heat 22% better at the factory-rated 450 horsepower when tested against the earlier 2017-2019 unit. At higher engine speed and load, the difference between the two coolers is even more apparent. 3300 RPM, 600 HP tests show a 31% greater heat reduction over the stock 2017-2019 oil cooler. The higher the horsepower, the greater the improvement.