<<I assume another aspect of longer oil changes is the filtration system? MB has a good setup, what about GM with the spin on filters? Is that setup agreeable with extended changes or not?>>
What are you on about here? MB has used spin-on filters in the past. With the abandonment of FSS, the '05 and later cars use a fixed 13K mile change using M1 0W40 with a fleece filter cartridge. And on shutdown, the filter drains completely, no waiting. RLE
