Engine oil for Yamaha 4-stroke

[hoavannguyen]

What is the best engine oil for 2003 Yamaha 4-stroke? I just purchased 2 100-HP Yamaha 4-stroke and cannot get a straight answer from the dealer. Which one would I use:<br />1. 10W-30<br />2. 10W-40<br />3. Mobil 1<br />4. Can I add any oil additive to the engine like Slick-50?<br />Thank for the advice.<br />Hoa

 

[seahorse5]

Re: Engine oil for Yamaha 4-stroke

Your owners manual and the service manual says to use 10W-30 or 10W-40. Do not use additives. Yamaha service says they do not recommend using synthetics since their motors are not tested for them.