I read this forum with great interest and learn new things. But I have an observation, manufacturer's have oil change intervals based typically on dino oil with factors such as overall maintenance schedules, environmental factors and engine life. I see people stating that dino oil is not good past 3000-4000 miles based on UOA. This invalidates manufacturer's typical recommendations of 7500 miles and sometimes 10,000 miles. When a manufactuer recommends a certain oil weight there are general charectoristics. I would imagine automotive engineers would as any scientist/engineer would take into account the worst case of oil, ie at 7500 miles, to come up with a recommendation of oil change interval. The average of the oil would be determined over the course of the interval not brand new out of the bottle. Personally I use 5000 miles based on the 6 month time period elapsing and always will with dino. I have had little issue with the succession of high mileage (250k) but cars I cared for using this interval. Just another thought to this accumaltion of info.