Oil Comparison: Synthetic vs Conventional and What Really Matters for Your Engine

When you're choosing engine oil, you're not just picking a product—you're deciding how well your engine survives the next 5,000, 10,000, or even 15,000 miles. Oil comparison, the process of evaluating different types of motor oil based on performance, viscosity, and longevity. Also known as motor oil selection, it's one of the most overlooked but critical decisions in car maintenance. Too many drivers think "oil is oil," but that’s a myth that costs thousands in repairs. The difference between synthetic and conventional oil isn’t just marketing—it’s physics, chemistry, and real-world engine behavior.

Synthetic oil, a chemically engineered lubricant designed for superior heat resistance, flow, and protection under stress. Also known as full synthetic motor oil, it’s made from molecules built from scratch, not refined from crude. This means it flows better in cold weather, resists breakdown at high temperatures, and keeps your engine cleaner over time. On the other hand, conventional engine oil, a refined petroleum-based lubricant that’s cheaper but breaks down faster under extreme conditions. Also known as mineral oil, it’s the standard your car came with. If you drive gently in moderate climates, it might be fine. But if you tow, race, or live where it gets below freezing, synthetic isn’t a luxury—it’s insurance.

Here’s the real question: does your car need synthetic oil? The answer depends on three things: your engine’s age, your driving style, and your climate. High-mileage engines often benefit from synthetic blends that contain seal conditioners. Newer cars with tight tolerances almost always require full synthetic. And if you live in the UK, where winters get damp and cold, synthetic oil’s ability to start smoothly at 5°C makes a bigger difference than most people realize. Even if your manual says "any oil meeting API SN," it doesn’t mean you should use the cheapest option. Oil degradation starts the moment it’s poured in—old oil turns to sludge, loses viscosity, and stops protecting moving parts. That’s why going over 5,000 miles between changes hurts more than you think.

What about oil additives? Do they help? Most don’t. The best oil already has the right blend of detergents, anti-wear agents, and friction modifiers. Adding more can upset the balance. Stick to the manufacturer’s specs—5W-30, 10W-40, etc.—and choose based on performance, not price per liter. And remember: synthetic oil doesn’t last forever just because it’s expensive. It still oxidizes, picks up contaminants, and loses its effectiveness. That’s why checking your oil level monthly and changing it on time matters more than the brand name on the bottle.

Below, you’ll find real-world guides that cut through the noise. From how long oil sits unused before it goes bad, to when synthetic oil actually hurts your engine, to what happens when you mix types—you’ll see exactly what works, what doesn’t, and why your mechanic might be pushing the wrong product. No fluff. No upsells. Just what your engine really needs.