I have had four GM 5.0/307 engines in Olds and Cadillacs. At about 170,000 miles they start consuming oil via the rings. I now have a new used RWD Cadillac Brougham with 62,000 miles. I've used Pennz 10W30 in most until now. I am going to synthetic 0W30 in the Winter, as I live in -30F northern MN and have one or two cold starts in that extreme temp. Love any ideas on making this engine go farther and not have the life cut short by ring problems.