I have a 2001 400ex stock. I don't know what the best oil is. Synthetic vs Synthetic Blend vs Conventional oils. I would like to run a 15w 50 viscosity, any problems with that? Thanks for your help.

400ex, azonic handle bars, promeg exhaust on order, with k&n power kit.

 

15w 50 full synthetic from mobil 1 is my personal choice.

make sure you run regular (mineral) oil during your break in time.

with the air cooled motor, the 400ex breaks down conventional oil at a rapid pace. more peace of mind with synthetic, epecially when pushing it hard.

 

I run Maxima 20w 50 in my 400EX, year round.