2002 Silverado 4.8l Oil Pressure Readings Flickering

[sicutlass455]

I have a 02 Silverado w/ a 4.8L 120K mile engine. I pamper the hell out of the Truck and I change the oil every 3K miles w/ synthetic oil (I change the manf; I buy whatever syn oil is on sale). Yesterday for the 1st time ever I saw the oil pressure guage need flicker during idle. The pressure has always been 40 lbs at idle to approx 45-50 when the rpms increase. Yesterday it dropped down to approx 28-30lbs only during idle. I'm thinking that it might be thin oil (i'm due for an oil change and will be doing it today), but has anyone ever experienced this problem?

 

Also noticed that the engine was one quart low on oil. It never ever burned any oil.

 

I'm the original owner and was very very upset when I saw this.......thanks for the help!!

[sicutlass455]

I just finished changing the oil and it came out like sludge!! The oil was as thick like cyrup in the oil filter and on the drain plug. After the oil change the oil pressure went up to 50 lbs at idle and 60 upon acceleration.

 

What could have caused the sludge?? The truck never overheated, but I did have to top off the antifreeze a few times because the LOW COOLANT came on. I did drive w/ the LOW COOLANT light on for a while, but there was always anitfreeze in the overflow tank.

 

I'm just very confused.

[jro909]

coolant is probably getting into the sump and mixing with the oil