1997 Eldorado, 83,000 miles. Well maintained, oil light on dash flicker. Digital display, stop engine. Tech changed oil pressure sender at oil filter location. check torque at crank. Replaced oil level sender in oil pan. Fresh synthetic blend oil change. 10/40. checked oil pressure with mechanical gauge, 30lbs cold, 15lbs after idling for 45 minutes. No oil flicker light on dash or digital display. After 2 hours of driving around town oil flicker returned on dash and stop engine display on digital dash. Odd no oil light was displayed during test, with sender removed and mechanical gauge installed. Anyone have any further suggestions?