1 quart oil or more per 1,000 miles go through the PCV system as oil vapour?

This would explain why in hot summer days I see negative fuel trims at idle + low load cells! See my thread "Fuel trims suddenly change?" http://teamzr1.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=639#Post639
Since I performed an engine cleaning + decarb procedure + orifice instead of the PCV valve the problem is solved

You have reason about the oil consumption in summer: I use a synthetic 5W30 oil and I need to add a quart every 1500 miles.

We don't have 10W30, the next quality oil 0W40, then 5W40, 10W40, 15W40 and 5W50.

What do you suggest?

The lower temperature in winter is 5F, the highest in summer 95F.

Yes all that oil going into intake will effect the fuel trims and I would suggest for summer heat is use like a 10W40.

Here we can see by 2004 GM did away with most of the PCV system as seen all the hosing from right head to left head is gone.
A plug fills the hole where PCV hose went to left head and only 1 hose goes into right head and then inside valley pan is 1 hose that then inputs fumes into the intake

Here is a C6 Z06 LS7 and it's PCV design which again is different then the other vette engines

After 3 weeks if having he PCV catch can in series with PCV and instake with a lot of WOT, bouncung the rev limiter and weather in the 80s this testing has ended with no more then 1/2 teaspoon of oil in the filtered can.

Due to the catch can system reducing volume flow we find it not worth it and took it off.

Same results we saw when we first tested these "Catch Cans" 5 years ago,