Pennzoil Platinum is a full syn. I chose it because multiple 3800 UOA's online showed low metals. I normally use Mobil 1 but that showed elevated iron and copper levels.
I found this, think it could be the issue?
Bulletin No.: 05-06-01-035A
Date: October 02, 2007
TECHNICAL
Subject:
L26, L32, L36, L67 Excessive Oil Consumption (Replace Exhaust Valve Stem Seals)
Models:
2005 Buick LeSabre, Park Avenue
2005-2008 Buick Allure (Canada Only), LaCrosse
2006-2008 Buick Lucerne
2005 Chevrolet Impala, Monte Carlo
2005 Pontiac Bonneville
2005-2008 Pontiac Grand Prix
with 3800 Series II, III V6 Engine (VINs 2, 4, K, 1 - RPOs L26, L32, L36, L67)
Supercede:
This bulletin is being revised to update the model years. Please discard Corporate Bulletin Number 05-06-01-035 (Section 06 - Engine/Propulsion System).
Condition
Some customers may comment on excessive oil consumption on 3800 Series II and Series III engines. An engine that has excessive oil consumption uses 0.9L (1 qt) of oil or more within 3200 km (2,000 mi).
Cause
This condition may be caused by the retaining ring on the exhaust valve stem seal not securely holding the seal on the cylinder head boss. If this occurs, the exhaust valve stem seal(s) may move off the cylinder head boss and no longer provide a sealing function between the exhaust valve stem and the valve guide.
Correction
Inspection and/or Replacement of Exhaust Valve Stem Seals
Follow the appropriate Service Information for the vehicle you are working on to gain access to cylinder head exhaust valves on both cylinder banks. Remove the engine valve rocker arm covers, the exhaust rocker arms and the exhaust valve springs.
