97 Sierra Z-71 Fouling Plugs On Cylinders 4 And 6 Only Using A Quart Of Oil About Every 5 Or 600 Miles I Typically Drive On Highway The Most I Have Changed Cap,plugs And The Wires Look Good.it Has 157,000 Miles On It.

Yes valve seals at their worst can cause this, are the plugs oil fouled? Possible intake gaskets also.

97 Sierra Z-71 Fouling Plugs On Cylinders 4 And 6 Only Using A Quart Of Oil About Every 5 Or 600 Miles I Typically Drive On Highway The Most I Have Changed Cap,plugs And The Wires Look Good.it Has 157,000 Miles On It.


FWIW I had to change the intake gaskets on my fathers 96. When I was pulling it apart I noticed it had a spot on the left bank where it was sucking in oil. That explained its oil use after I replaced the stock PCV with the fixed orifice type with little improvement.

Worth a look and if the intake gaskets have never been done I would start there after I ruled out the cylinders with a compression check.