10w30 or 25w40 for pro XS200

[Jetch114]

Serial # 3B099541

Reading over my manual and I’m seeing either 10-30 or 25-40 synthetic blend are acceptable oils to use in my motor. Do you folk prefer one over the other and if so, how come? Dealership sent me home with 25W-40

[Pulsare2020]

I have a 300R, but my manual appears to suggest that the 25W-40 is preferred in all the Sea Pro models and all others are 10W-30 semi-synthetic. However, as you suggested they also say that you can use 25W-40 as an alternative in the non SeaPro engines, but it sounds like the 10w-30 is preferred. I think the thinner oil would flow better to engine vital parts on cold start up, and have slightly less horsepower drag. I think Mercury would honor the warranty with either choice if it is their oil. Perhaps if you do most of your boating in 90*- 105*F weather and run very hard, the heavier oil might provide a bit better viscosity protection.

[EuropeanAM]

10w30 Synthetic Blend.

I would not recommend 25w40 for Non-SeaPro Models UNLESS the engine is operated in extremely high temperatures that cause lower or unstable oil pressures.