Useful Car Tips

Synthetic vs. Conventional Oil: What’s the Difference?

August 07, 2018
Is your car due for an oil change? Most lube shops recommend an oil change every 3 months or 3,000 miles, but it’s always a good idea to check your oil level between changes to make sure your car engine has enough lubricant to stay healthy. When you’re at the lube shop, they might ask you if you want conventional or synthetic oil. Do you know which one is best for your car? Keep reading to find out!

Conventional Oil Characteristics

To understand the differences between conventional and synthetic oil, let’s first establish a few things about motor oil in general. Conventional oil is produced from crude oil, and has a specific viscosity, Total Base Number (TBN), and weight. The viscosity of an oil describes the hydrocarbon bondsapparent in the oil itself. If the hydrocarbons are cool, they group together, therefore making the oil thicker. Hot temperatures will spread the hydrocarbons out, so the oil becomes more liquid-like. The TBN of an oil denotes how acidic it is. The combustion processes that occur in your engine—and allow it to function in moving your car—create acid, which is soaked up by the alkaline oil. When the alkalinity of an oil has become too acidic, your oil loses its function and your engine may be at risk. The weight of an oil is part of the designation you’ll typically see at auto parts stores. Most vehicles take 5W-30 oil. But what do those numbers really mean? Well, the first number before the W stands for the Winter weight. The second number denotes the viscosity at 100°Celsius. Typically, 5W oils are thicker at winter temperatures than 10W oils are.

The Synthetic Difference

However, according to Road and Track, when 5W-30 conventional motor oil is brand-new, it acts “exactly like a 5W-30 synthetic motor oil.” So, what’s the difference here? Well, on a base level, synthetic motor oils are, from the start, a better oil. Made via the Fischer-Tropsch process, which was created by Germans during the Second World War, synthetic oils are refined further than conventional oil. Grouped in the III-V designations of oil, synthetics are a step above Group I and II, which comprise the conventional oil groups. What this really means in layman’s terms is that there are certain additives in all oils, but when you start with a more-refined base, you’re going to have a superior oil. Synthetic oils do not degrade as quickly as conventional oils do, and in fact can be used as a “salve” for older, sludgy engines. All oils will end up degrading over time, but synthetic oils move at a slower rate than conventional oils.

Which Oil is Right for Me?

If you’re not sure which oil to choose, check your owner’s manual. If it does not specify that you need to use synthetic, save yourself a couple bucks and continue to use conventional oil. However, if you own a sporty or performance car, it is often a good idea to invest in better oil. Performance parts can be expensive to replace, and at higher temperatures, your engine will need all the protection it can get. Feel more confident about your oil knowledge? Try it out the next time you find yourself at your local lube shop!
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