2000 GMC 5.3L - using oil

[gkh7890]

Need some help before I put out the $$ to get it diagnosed and repaired. I have a 2000 Sierra w/ 5.3L v8. I now have 222K miles on it. Used Mobil 1 (regular) oil for the 1st 12K miles and then Mobil 1 synthetic ever since.

Since 207K miles, I've noticed the oil is being used up/burned etc. Upwards of 4 quarts b/w oil changes. There are no drips on the driveway, no smoking out the exhaust. Is this an intake manifold issue or a cracked head? I'm assuming the oil is going into the antifreeze?

I'd appreciate some input.

Thanks!

[maxwedge]

Oil consumption can be caused by a multitude of issues, the lack of exhaust smoke does not mean that it is not just burning oil, as the cat and combustion chamber burn it off before it is visible. Bad or wrong pcv, worn valve guides and /or seals. bad oil rings, scored bores, excess bearing clearance,` leaking intake gaskets at the ports, to name some possibilites. Oil in the coolant would show in the jar or radiator, I don't think so, your system would be overfilled.

[Z15]

I recall reading or hearing about pcv problems with some of these early engines. There is a new valve that is supposed to be fix the issue.

[gkh7890]

Maxwedge & Z15,
Thanks for your input. Sorry for the delay. I spent some time reading thru my Chilton's manual and I'm planning to get a vacum gauge and check out my pressure readings to see if I can further diagnose it before I take it to a mechanic (dealer??)?

Any experience with this?

Thanks again and MERRY CHRISTMAS!!!!!