BoostnBenz, I think Mobil 1 is 15w-50 not 40 . I use it as well but I don't see why they would not mix.

In the last two days it's been in the low-mid 20's here, usualy in this it starts well in this but this time I had to glow for two 30-second sets and crank for about 20 seconds before 2 or 3 cylinders caught at half throttle. The other cylingers caught on after about 30 seconds. After that, it runs like a real gem. I thought adding some 0w-40 might help this.