Anyone else experience this phenomenon?
OK. Just got back from a 1200 mile drive from Las Vegas, NV, to Farmington, NM, Gallop, Flagstaff, AZ, Kingman and back to Vegas. Averaged about 24 mpg with my Fiancee and in her ’93 TT. 184,000 miles and it ran flawlessly all the way.
Just one concern though.
It seems that every now and then the oil pressure gauge, which usually points to 2:30 98% of the time just below the little icon, would slowly began to drop until it would point to about 4:00 position. I would back off cruising speed of 65 to 75 and it would slowly move back up to its normal position and stay there for sometimes an hour at a time before exhibiting this behavior again.
Oil full up with 15w-50 Mobil One plus some “No Smoke” that was added to pass the last smog inspection.
It seemed to do it more often while going on uphill grades but not always. It may also exhibit this behavior only once in an hour of driving and sometimes within ten minutes of the last episode. Slowing down for about 15 seconds would always bring it back up. Engine RPM’s were typically between 2,400 and 2,700 in fifth gear.
Acts like there might be some blockage of return oil to the pan but the oil is always unbelievably clean for an engine with this mileage.
It also occurred to me that it might have something to do with the oil temp sensing device that causes the oil to be bypassed through the oil cooler if it get hotter than it should be. If the oil cooler has some restriction in it then that could be a cause of the drop in “indicated” pressure whenever bypass is active.
Only other thought is a possible loose connection of the wire on the sending unit itself, but that should not be affected by any rpm variance like slowing down a little to cause the pressure to rise again.
Even though the average temperature along the way was anywhere from 32 degrees to 60 outside so the air was really cool all along the way. Engine coolant temp never varies and has “Water Wetter” in it.
Any takers on this one?
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