I'm willing to consider evidence showing some properties of oil are improved with age. I'd love to see the actual SAE papers referenced previously. I also think it's fair to claim too frequent oil changes are costly and unnecessary if you can back it up with evidence. But I wonder if extrapolating the test results to claim that too frequent changes are harmful is correct. I'd be very interested in data showing an engine failed prematurely due to too frequent oil changes.

FWIW our fleet vehicles regularly see 300k plus miles on original engines, both diesel and gas, with 3k mile oil changes. It's the bodies, not the engines, that usually take them out of service. If the 3k mile oil drain intervals were detrimental I'd expect to see differences between the bulk of the fleet and our three '04 Sprinters which have drain intervals ranging from 7k to 10k miles depending on oil used.