In the cold temps. I have trouble with my bike not warming up. I switched from 10w-40 to 5w-30 (Mobil 1 5w-30) and it warms up correctly. It is around 35 degrees right now, and would like to know at what temperature I should switch back to a heavier oil. The Mobil 5w-30 bottle says it will protect at oil temperatures of up to 420 degrees, so theoretically I could use it all year round. Also Im running a 9 plug, because that is what the manufacturer reccomends for my 125. Would switching to an 8 help? Could this hurt the motor? Thanks for any help.