Here is the difference between conventional and synthetic oil


It’s an age old question: Is there any benefit to running synthetic oil over conventional oil in your engine? I think we can safely say that for the vast majority of internal-combustion engines on the road today, the answer is yes. So just how does the synthetic stuff deliver on its promise of additional protection? Thankfully, the crack team over at Donut Media’s Science Garage provide us the lowdown on the differences between conventional and synthetic motor oil.

The host for this 15 minute science presentation, Bart, begins by providing a quick look at the average oiling system. Comprised of the oil pan, oil pump, pressure regulator, and oil filter, the components work together in dispersing the slick oil throughout the engine’s reciprocating parts. Oil is needed to provide lubrication to critical areas, otherwise the heat generated through friction of metal-on-metal contact would result in the engine seizing up.

Speaking of heat, it’s important to understand how oil behaves at different temperatures. Bart dives in, explaining how the lubricant’s viscosity—which can be simplified to resistance to flow—is vital to an engine’s survival. Cold oil becomes more viscous, slowing its flow and increasing its thickness, inhibiting the fluid’s ability to penetrate small, tight areas. On the flip side, heated oil loses viscosity, becoming more water-like and thereby losing much of it’s lubricating qualities.

Luckily, scientists discovered a way for motor oils to hold onto those desirable properties for a wider range of temperatures, creating what’s known as multi-weight oil. In Bart’s example, 5W-30 motor oil acts like a thinner 5-weight oil at lower temperatures while simultaneously flowing like a 30-weight at higher, operating temperatures. Of course the actual oil itself is neither a 5- nor 30-weight, but the viscosity curve it follows over varying ranges of heat mimics parts of both straight-weights.

Now that the basics are out of the way, Bart’s able to discuss how this info ties into conventional versus synthetic. Due to their laboratory-created nature, synthetic oils contain fewer imperfections and greater molecular uniformity. That’s great if you have a PHD, but what does that mean in the real world? Well, it just tells us that synthetics are more resistant to breaking down in high-heat and flow better than conventional oil at icy-cold temperatures. They’re also just plain more resistant to degrading over time, providing more protection for your engine for more miles.

But as with most things in life, there is a drawback—cost. Synthetic is more expensive on average, however the price disparity can often be offset by the increased interval between oil changes. So should you be running synthetic in your car? In many applications it would probably be beneficial, but be sure to consult both your owner’s manual and oil manufacturer’s specifications prior to pulling out that funnel and pouring it in.

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