Low Oil Pressure When Cold Outside

1999 Silverado

I kept getting a low oil pressure warning and the gauge was bottoming out when I went to a stop. If you hold the brake and rev the engine you can bring the pressure back up. I originally was using 5w 30 oil but chaged to 10w 30 thinking that would solve the problem. This only happens on a cold day outside (30 degrees) and it only drops when coming to a stop after the engine has warmed up. Any suggestions on where I should start.

Thanks

First off is your truck making any noise{ping\knock} at idel If not use a manual oil gage and check if you have presure if you have between 30-40 at idel your oil sending unit is gone if you have little or no presure your oil pump\pick up can be gone or your oil filter is wrong or defective. There is so many things it can be but if the motor runs good and there is no noise{mostly knocking} chances are it is a oil sending unit. Worse case if the motor is a high miler the mains could be worn this will give you little oil presure at idel but when you rev the motor the presure will increase. hope this helps