I bough 2005 Express 4.8 with 141000 miles, when i turned the eng. the oil pressure went to 39psi and gradually dropped to less than 10 psi. I turned the engine off for 10 to 15 second and i turned the engine back on, the oil pressure went up to close to 40 psi the start dropping again to less than 10 psi.
I replace the oil pressure sending unit no success, is doing the same thing.
before i install the new sending unit i replace the oil and the filter, I put 5w10. any advice?

 

Welcome to the forum. Good to have you on board. Be sure to visit the Express section. If you post your question there, you'll get more views.