I have a ample supply of Motorcraft oil,syn-blend & full synthetic,any thing WRONG with a 50/50 mix of 5w20 blend & full synthetic for a 2003 f-150 5.4 triton ???
Nothing bad will happen to your engine with mixing MC oils. But, if you have plenty supply of each for an oil change why don't you use syn-blend for spring&summer and full synthetic in fall&winter ?
