So last night I did a oil change on my 2005 Chevy Silverado 1500 and I put 15w40 in because it’s over 230000 miles and that’s what my mechanic told me to And the oil pressure is around 60, should I be concerned?
My oil pressure is that high when I first start the motor, but slowly drops as the motor heats up. I drive it to warm it up, careful not to overload it beyond 80 before it's warm. I don't think you should worry about it, but in the future, I would not put that oil in it.
Old timer mechanics would often change the oil weight with mileage and/or weather conditions, but technology has come a long way in both oil and engine manufacturing, tightening tolerances. I don't think engines these days are as tolerable to oils that they were not designed for. They make, "high mileage" SAE 5W 30, that I would use for high-mileage vehicles, rather than using an oil that's not spec'd by the manufacture.
Partly depends on what pressure was with the correct oil. 60 psi sounds high depending on RPM. However modern engines are designed with close tolerances. Engineers who designed the engine intended a certain amount of oil flow across the bearings to cool them. Shear in the oil film causes heating. There is less cooling oil flow across the bearings with high viscosity oil. Ambient temperature also has an influence. I use the oil viscosity the engineers designed for rather than hearsay.