Royal Purple11629 HPM FC-W Multi-Vis 40 High Performance Synthetic Marine 4-Stroke Motor Oil - 1 Quart

Great oil! Finally a Marine Synthetic I can trust. My marina previously had been changing oil in my twin Mercruiser 350 Mags with what I thought was a full synthetic. Apparently, finding full synthetic Quicksilver/Mercruiser oil is hard and very expensive, so my marina was using a blend. Let me tell you, there is a HUGE difference between a full synthetic and a blend. Full synthetic does not break down in your engine like conventional oils do. In the marine environment, and the constant stress a marine engine is under, you want full synthetic. After about 25 hours on this oil, my engines are running a bit cooler at WOT, and I seem to have gained some gas mileage at cruise. I have also noticed my starts have been much smoother, with the engine cranking over MUCH easier after switching to this oil. I am confident I will get a few extra years on my engines running this oil!

Good Synthetic marine oil. Used in an almost new 9.9, 4-stroke outboard motor. Switched to this from Amsoil and motor is noticeably quieter.

Time will tell but initially engine runs quieter in my Sea Ray. Needed an alternative to Mercruiser 20-40 and this is it. Customer service at Royal Purple is very responsive. Tests of their oil indicate it is an exceptional product.

Couldn't locate Amsoil marine oil so RP it is. My 4-stroke marine outboard won't know any difference. Merc/Quicksilver are priced similar and since Amsoil/RP actually have oil analysis's studies posted everywhere, its an easy choice me.

It is the only oil that will work with our boat motor, does a great job and ordering it through Amazon was fast and very convenient versus going to a store, Most stores don't carry this brand anyway, even Bass Pro among others.

I used this in my 20hp outboard boat motor.

We use Royal purple for our cars and boat motor. It is important for the life of any engine to have the best oil. I would recommend this product to others.

I run this in my 4 stroke 225 and it is awesome. You are not going to find it this cheap anywhere else on the web!

Good.