Mobil1 user...

I bought my car with exactly 60K on the ticker and swapped the oil...I'm right at 270K with no oil comsuption. I pour in 5 qrts and get back 4 after 3K miles. I do NOT baby this car. Ask my brother...

I also use Lucas Syn Stabilizer Additive.

I know a guy from another forum that pulled his LT1 heads at 125K to rebuild his engine...needless to say, the engine still had its cylinder honing from the factory. Basically, the engine was still breaking in! Another Mobil1 user.

Bob the oil guy has good material when it comes to oils, filters and additives...its where I would start.

From what I understand, the best combo is Mobil1 + Mobil1 Filter or K&N filter (they are the same).