2004 2500 hd Silverado 6.0 looses 2 quarts of oil driving 350 highway miles. 90,000 on engine. I can not find were it went. Any ideas.

[Doug111]

2004 Silverado 2500 hd lost 2 quarts of oil driving 350 miles and can’t find were it went. 90,000 on engine. No oil in radiator or water in oil. No evidence of oil leaking. Any ideas!

 

[zora]

Have you had the vehicle on a lift to check for leaks?
Any blue smoke when starting or when letting off gas pedal?
Do you have a check engine light on?

 

[Doug111]

Can’t find any leaks, no smoke out of exhaust and no engine code.

 

[zora]

Try compression and leakdown test.
What viscosity oil do you use?

 

[Doug111]

5w-30 full synthetic. Ok I will.

 

[zora]

Have you tried a new PCV valve?
There was a technical bulletin concerning switching to a fixed orifice PCV.