Oil for Suzuki Eiger air/oil cooled 400

[454MAG]

Looking for a good oil for this machine. It will be changed frequently due to riding thru deep water and mud. Avg about 80 mi per ride and will change oil after 2 rides. I usually have a good stock of M1-15-50 on hand but dont know if a little thinner may be better. I know it gets hot because the electric fan comes on frequently. This machine has the clutchless manual transmission. I may even consider a Heavy duty Dino oil like Delvac 1300.
Any opinions ?
Ted

 

[tmorris1]

If you are dead set on changing the oil every 160 miles, then I would not use an expensive synthetic. I use 0W40 Amsoil in my Polaris, but many people have good luck with Rotella diesel oil for a reasonable price. What does Suzuki call for in the manual?