Synthetic engine oils are routinely promoted as providing superior performance to conventional oils. The American Automobile Association (AAA) recently set out to validate these claims by conducting independent research into differences between conventional and fully synthetic oils. The results were released this week.

The AAA study compared five engine oil brands, commonly available in the United States, using eight ASTM tests including: shear stability, deposit formation, volatility, cold temperature pumpability, oxidation resistance, and oxidation-induced rheological changes. Engine oil brands were only considered for evaluation if they offered fully synthetic and conventional oils and met ILSAC GF-5 and API-SN specifications.

To administer the tests, AAA engaged two independent (International Standards Organisation) ISO 17075 certified testing laboratories with considerable experience in ASTM testing for engine manufacturers and oil companies.

The results of the study are probably in line with expectations. With the exception of ASTM D4742, fully synthetic oils outperformed conventional oils in all ASTM tests, exhibiting an average 47% improvement. The research appears to support marketers claims of improved engine oil performance from synthetic oils, albeit at a higher cost. According to AAA Approved Auto Repair providers typically charge USD70 for synthetic oil changes, USD32 more than a conventional oil change.

Of greater concern to suppliers of synthetic engine oils were consumer trends uncovered as part of secondary research, wherein 44% of respondents said they did not believe synthetic motor oil was better for their engine, or were unsure. The price of synthetic oil is also preventing greater uptake, 43% of drivers using conventional oil for oil changes do so because synthetic motor oil is too expensive.