Synthetics were developed with petroleum-based lubes’ shortcomings in mind and were specifically formulated to withstand harsh aviation engine demands. To this day, synthetic lubricants are the standard in the aircraft industry because of their ability to perform in such harsh environments. Since AMSOIL (my personal choice of lubricants) introduced the first synthetic oil for automotive use back in ’72, synthetic lubricants have become increasingly popular because of their excellent lubricating properties, greater ability to flow at cold temperatures, and their ability to withstand high temperatures for extended periods of time. In fact, more and more new cars are being delivered with synthetic oil in the crankcase – and also require synthetic oil use throughout their service lives.
From what I understand, the two primary differences between synthetic and conventional petroleum oils are the base stock (the liquid that makes up the volume of the oil), and the additive package. There are additives (not to be confused with over-the-counter parts store stuff) in all oils that enhance the wear-resistance properties, the ability of the oil to neutralize acids and combustion by-products and provide corrosion protection for the engine’s internal surfaces. The amount and quality of these additives vary from one brand to another and are critical factors in the ability of any oil to adequately protect an engine in varying driving conditions. As a rule of thumb though, you’d figure the cheaper the oil, the fewer additives it has and therefore, the less able it is to protect your engine.
One reason synthetics are deemed superior is that they almost always have more and higher-quality additives than standard petroleum-based products. Another is that the synthetic (versus petroleum-based) formulations enable them to last many times longer than conventional oil before they begin to degenerate. The synthetic base stock, however, is at the heart a synthetic oil’s ability to flow at cold temperatures and withstand greater amounts of heat over significantly longer periods of time.
Petroleum base stocks are sensitive to stress and heat. Additionally, various waxes that are contained in all petroleum products, regardless of how well refined they are, cause oil to thicken or jell at extremely cold temperatures. At the other end of the temperature spectrum, high-engine temperatures and heavy loads (as typically found in towing or high-performance applications) cause these lubricants to break down and the conventional base stock of petroleum actually boils off – causing viscosity breakdown and sludge formation. And check this out – this can happen at temperatures as low as 230 degrees, and in fact, by 250 degrees many petroleum oils will already be suffering significant breakdown.
This Summit Racing Equipment offering (part #SUM-G4960A) is a good representation of an af
Synthetic oils, on the other hand, are engineered specifically to provide all the lubricating properties that natural oil possesses, but none of the cold thickening or hot thinning properties of petroleum oil. Synthetics are formulated so that they can withstand prolonged temperatures of 300 degrees and still protect your engine. In fact, the American Society of Testing Materials (ASTM) standard wear-resistance tests are conducted at 302 degrees, and in those tests synthetic lubes outperform petroleum lubricants by a factor of 4:1 and sometimes more. The point being, synthetic oils have a much wider operating temperature range by design than petroleum oils, but performance engines will benefit from an engine oil cooler, so don’t think cuz you run synthetic oil that you can take a pass. This said, an engine oil cooler is an accessory that we should seriously consider, especially since its cheap insurance relative to our overall street rod investments.