2001 Screw 4.6 The question I have is when the weather drops into the low 40s and colder the oil pressure gauge doesn't move and the dummy light come on. This only happens when it's cold out and once the engine is running for a few minutes it starts working. Am I in need of a sensor or something ?

 

What weight oil are you using?

 

You need a new oil pressure sending switch.

The oil weight is irrelevent in this case.

Steve