I read something once about a guy who changed oil for Mercedes at the dealership. He said that most of the cars were using synthetic oil and had it changed around 3-5k miles at each interval.
When he would run a test on the remaining life of the oil, he found that it was usually only degraded about 20%. So, he would always use that oil in his own cars and hadn't paid for oil in years.
He might have been full of it but I do think most people seem to change the oil too soon.
If we can all agree that most dealerships/car companies tell us to change the oil every 5k miles and those companies are usually conservative with their reccomendations, why would we do so sooner?
For the longest time, I would change the oil every 3k miles but not anymore. I change it at 5k and use synthetic. Haven't run into one single issue in three cars now.
Other crap has broken but by the time I sell the cars, the engine is still running perfectly.
