I believe that oil matters a great deal.
1991 SHO, 21 years, 416,750 miles, changed OEM rod bearings at 258,000 miles, have used only Castrol GTX (High Mileage for a while) 10W-30 at 3,000 mile intervals. No sludge and the cam lobes still looked great during the last gapping service at 405,000...