I don't believe that going 8K-14K between oil changes is good for an engine.
I have personal knowledge of a Class 8 diesel going One MILLION miles without an oil change using a part synthetic.
IMHO to blame a MINUTE oil specification on engine failure is nothing but a cop out and is purely profit motivation driven. Blame it on the consumer and you void an expensive warranty claim due to design flaw. Keep the consumer AFRAID of voiding a warranty claim keeps dealerships in business!
Oh, and I have ran a GEO METRO 15,000 miles between oil changes.....I sold it with 450,0000 miles showing on the OD.....head replaced twice due to burnt valves...typical for the 3cyl design.
The concern of the above diesel was that it would not have all other components subjected to wear properly maintained simple because the said components would be serviced at a typical oil change interval and unless the routine interval was observed those components might no get proper maintenance. The only adverse effect was that hydro carbon emissions went up with mileage. The EPA monitored this test and the emission level stopped the wide spread adoption of a new standard......this was in 1995!
IMHO there is no real reason that a gasoline engine of modern design should not be able to exceed 50,000 mile oil change interval. My belief is that profit is the goal and not longevity.
GM came out with a 'new' specification for the simple reason that it NEEDS the money from frequent dealer visits to be profitable.
IN these discussion I've been accused of many things, but I'm not attacking GM. These tactics are nothing new. Mercedes or you name the high dollar marque has been using these tactics for YEARS!
It's all about maximizing profit without and real improvement in design.