Presure oil with my 1998 gmc sierra

GM oiling systems are likely the best around. I spent a lot of time building them...Though I'm sure that someone will argue that 15psi is fine, I prefer to see no less than 30psi running at idle (can go as low as 20 safely) and 45-65 at 2,500rpm. (but 40 is also fine) Synthetics tend to lower those numbers by about 5psi but offer better protection so there is no sacrifice. Old very hot, or fuel contaminated oil will run considerably lower but changing oil will eliminate that kind of problem. Bearing wear will lower pressure as bearings actually seal most of it against the crankshaft except for a small amount that by design escapes and oils the cylinder walls.A partially obstructed pump screen can also lower pressure as well as volume. Have pressure tested with a mechanical gauge. Often the dash gauge can be off by as much as 5psi. Once actual pressure has been verified, you can take steps to correct it.
Low oil pressure shows itself first by causing valve lifters to become noisy (why I mentioned taping noise) If you have any noise, it is critical that you don't ignore it or it may cost you an engine. However if it's not noisy chances are you just have a bad sender that is giving you incorrect readings. GM oiling systems are likely the best around. I spent a lot of time building them...Though I'm sure that someone will argue that 15psi is fine, I prefer to see no less than 30psi running at idle (can go as low as 20 safely) and 45-65 at 2,500rpm. (but 40 is also fine) Synthetics tend to lower those numbers by about 5psi but offer better protection so there is no sacrifice. Old very hot, or fuel contaminated oil will run considerably lower but changing oil will eliminate that kind of problem. Bearing wear will lower pressure as bearings actually seal most of it against the crankshaft except for a small amount that by design escapes and oils the cylinder walls.A partially obstructed pump screen can also lower pressure as well as volume. Have pressure tested with a mechanical gauge. Often the dash gauge can be off by as much as 5psi. Once actual pressure has been verified, you can take steps to correct it. Low oil pressure shows itself first by causing valve lifters to become noisy (why I mentioned taping noise) If you have any noise, it is critical that you don't ignore it or it may cost you an engine. However if it's not noisy chances are you just have a bad sender that is giving you incorrect readings.