So ive got a 01 2500hd 6.0 that sometimes will use oil. I can drive it around town for months and not use a drop. Then all of a sudden a 3 hour freeway trip will cause low engine oil light to come on. But only sometimes? The truck has about 130,000 on it. Im almost thinking its a pcv issue that maybe only happens when there is alot of vacumm? I installed a new pcv valve a couple years ago but it didnt help. What do you guys think

 

It could very well be the PCV. Most guys install a catch can to try and cut down on the oil being ingested into the engine. If you look inside the intake is it super oily? How do the plugs look?

 

I put a catch can on my 04 and it seemed to help.
High RPMs will make the problem more aggressive