I have a Harley sportster in which I'm running a mix of 50% Pennzoil 20w50 (conventional dino auto oil) and 50% Royal purple 20w-50 synthetic motorcycle oil. The oil has only about 1500miles on it and I thought I would wait until the early summer and then change the oil over to Valvoline at that time. Unfortunately, we here in the midwest are having an unseasonably cold late winter / early spring with temps ranging from 25F to 35F. Despite the 50% synthetic RP, is this oil not right for the lower temps? Or will be ok for 200-300 miles until spring (hopefully) makes it appearance. If its not right what weight? 10w-40?