I have been using synthetic oil in our family cars and my Harley for more than the last 15 years. For many years now, I have been using Mobil 1 5W-30 in all the family cars and changing at 3,000-4,000 miles and using purolator filters. For the Harley its been Redline 20W-50 and Perf-form filters, with the interval 1500-2000 miles. My thinking has been, for the m/c cost is no object, but for the cars Mobil 1 at $4 is pretty darn good verus the $8/qt Redline. In reading stuff on this website, it seems to suggest that the real premium synthetics do have increased additives permitting a more longer chnage interval. I'm also not getting any younger and if I could cut # of oil changes per year, with no loss in protection, it would be a good thing. So here's my question: Would Redline 10W-30 with changes at 5,000 miles offer the same or better protection as Mobil 1 5W-30 with changes at 3,000. With this approach the cost would be the same as with Mobil. Of course, I'm talking about the cars only.