Marine Synthetic Motor Oil FAQs
HPM is Royal Purple’s high performance synthetic engine oil designed specifically for marine applications. It is engineered to reduce operating temperatures and boost torque and horsepower while you’re out on the water. HPM engine oils are full synthetic and contain our proprietary Synerlec® additive technology.
When looking at a SAE engine oil viscosity grade, the last number is most important. HPM oils are intended for 4-stroke, gasoline marine engines.
If the factory recommends 5W-30, 10W-30, or SAE 30, Royal Purple HPM 10W-30 is the best choice.
If the factory recommends 5W-40, 10W-40, 15W-40, 20W-40 or 25W-40, Royal Purple HPM 10W-40 is the best choice.
When looking at a SAE gear oil viscosity grade, the last number is the most important. If the factory recommends 75W-90, 80W-90, or SAE 90 (straight 90 weight) gear oil, Royal Purple HPM 80W-90 will work great in your lower unit/outdrive.
For 2-stroke engines, we recommend Royal Purple HP 2-C two cycle oil. It works great in pre-mix or oil injected applications. For pre-mix applications, we recommend using the manufacturer recommended mix ratio.