I'm also in Colorado. I use BMW full synth 15W-50. I also use their synth gearbox lube.jvreschar said:Thanks for the info. I am definitely going synthetic, I run it in all my vehicles. My bike has 25K , which viscosity on the upper end 40W or 50 W would you recommend. I live in Colorado so it can get a lot colder than I am willing to ride in.