Where's My Oil Going...?

[Yukon5.7]

Recently I have noticed that my 99 Yukon has been loosing about 3/4 of a quart of oil about every 500 miles. I'm lost the truck does not burn oil going down the road. There are no signs of leaks. Where else can it go..?
I have also noticed the lifters will knock on a chilly morning.

 

[grnrpr68]

if its not leaking on the ground or on the motor then you probably burning it out the tail pipe

 

[h0tr0d]

It's hiding from you...waiting to spring forth and soak you next time you crawl under the car. lol

If there aren't any drips on your driveway, check underneath the car and look for buildup on crossmembers etc. if it's coming out in a mist while you're driving down the road. Otherwise, you're burning it.

 

[steamroller]

It can leak into the radiator if you have the factory oil cooler

 

[Danny_Z56]

Take a look at your coolent and make sure their is no oil in it.

Otherwise i am stumped.

 

[BWdiver]

Like the others said, if its burning the oil let it idel for 15 to 20 mins and have someone get in side and rev it up and look at the tail pipe to see if you are getting any trace of white or blue smoke if you are your rings are going bad more than likely.