Originally Posted by former NXMX5
i wouldn't advise running that thick an oil in the car. they obviously want the super low viscosity for something, and if you go to a 15- its gonna take a l o n g time for the oil to get pumped up to the top of the engine. especially now that the winter is coming. if you're ever going to use a heavier oil, do it in the middle of the summer.
The "border line pumping" of the oil is the real concern.
0W-XX is about -20 deg. F,
10W-XX is -4 deg. F
15W-XX is +5 deg. F
20W-XX is about 15 to 20 deg. F
If the cold crank capability of the pump can not handle a heavier oil then you will have a dry start of the engine. Also, depending on how the pump was designed, it may not be able to handle a heavier oil and literally destroy it's self. Knowing that all of the auto manufacturers are designing for better fuel economy, components are getting lighter, I wouldn't recommend jumping 3 - 4 grades of oil.