2004 GMC Sierra

Engine Mechanical problem
2004 GMC Sierra 6 cyl Two Wheel Drive Automatic 80000 miles

Oil gauge is flunctuating. When driving gauge shows 40-45, but when slowed down or at a stop, the gauge is 20-25 & sometimes 15-20. Then when speeding up gauge goes back to 40-55. If let off gas, goes down to 30 & back to 45 when back on gas. Oil sender unit has been replaced, but stiil acting the same. No noises from engine, & no real changes in how the motor runs. Seems to run ok. Would appreciate any info that might help. Thanks *
June 5, 2010.

Check the oil pressure with a mechanical gauge, if normal replace the oil pressure switch. If abnormal could mean oil pump and/or engine bearing.

Jun 5, 2010.