What is you engine oil weight? I had someone put 5W-30 in my old Buick with 125,000 miles on it. Warning light on start up, and when in the mountains, got a low warning pressure message. Changed to 20W50 and no more issues. If you use it for work or long drives in hot weather, go with a heaver weight. The swing of 10 pounds is normal. You may consider changing out the sensing unit to see if that may cause a miss reading. Think of the oil as water vs. sirup. That may explain the reason at normal temp, the indicator reads 25 and when you increase the engine AND pump speed, it moves up to 30. Ask around with others that own your year and model, and use it the same way on their oil weight and pressure readings.
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