European drivers change oil far less than Americans, with apparently few negative consequences. Since the 1980's, many US auto manufacturers have relaxed the intervals for oil changes to as long as every 5000 or 7500 miles, replacing the three month/3000 mile standard recommendation.

On the Other: Synthetic lubricants

Some experts claim far fewer breakdowns in the lubricating properties of synthetic oil and that friction surfaces show significant decreases in wear. However, in-service tests of both types of oil can show that the ability to protect and lubricate internal engine surfaces does occur. With synthetic oil, it happens far later and to a lesser degree than with conventional oil.

Bottom Line

Synthetic oil has compelling arguments for its use. Independent laboratories can test small samples of oil, analyze the substance and provide a written report with an expert opinion. Results will state whether the oil was overused, still has plenty of service available, what foreign materials are in it (contaminants, water, metals from bearing surfaces, etc.), and can do this relatively inexpensively. Since cars are driven and used differently, experts state that only oil analysis will reveal its limits and indicate what the "average need" is for oil change intervals for each application.

Source:

Consumer opinion

Synthetic oil analysis case study

Expert opinion on "average need"