I just picked up an 05 6.0 Power Stroke. I'm seeing quite a few proponents of 10w-30 for these engines,and the manual states this viscosity is ok up to 90° ambient. I plan to tow in temps exceeding this level (Phoenix, AZ), so I'm wondering why Ford specifies that limitation for 10w-30? I can't imagine the oil temp at full operating temp being any different between 15w-40 and 10w-30, even at 115° ambient. If this engine is shearing 40w oil anyway, seems like I might just be as well off with 10w-30 year round, and enjoy the cold start benefit.
Does anybody here use 10w-30 in hot climates in their 6.0?
Does anybody here use 10w-30 in hot climates in their 6.0?