Hi everyone, I was just curious as to what brand of oil and what weight oil people would recommend for my 2006 WR450F. I typically ride in weather between 60-95 F. My manual says either weight will work, but which would be ideal for a newer engine? As for brand, I am leaning toward switching to a full synthetic like Amsoil (MCF) motorcycle 10-40 or maybe Mobil 1 MX4T motorcycle 10-40. Neither of them come in 20-40. However, You can get both Amsoil and Mobil 1 in 20-50. Currently I am running Yamalube Simi Synthetic 20-40. The thing I'm concerned with is in my owners manual it says not to use oils with a friction grade of CD or higher and I believe both Amsoil and Mobil 1 have a grade of CD. Is this just something Yamaha puts in the manual to keep riders using Yamalube or is this a genuine concern? I was looking on the amsoil website and it says it is fine to run with all Yamaha Motorcycles and will not void the Yamaha warranty, not that my 30 day warranty is still in effect anyway.