Every oil bottle has a code on it, 5W-30, 0W-20, 10W-40, and it's easy to treat that as just a label rather than something with a real, specific meaning. It actually describes exactly how the oil is designed to behave at two different temperatures.
The First Number: Cold Weather Performance
The number before the W describes how the oil flows in cold temperatures, specifically how it behaves at engine startup before things have warmed up. The W itself stands for winter, not weight, a common point of confusion. The lower that number, the thinner the oil stays when cold, which means it flows faster and reaches critical engine components more quickly right after startup, exactly when an engine is most vulnerable to wear from inadequate lubrication.
A 0W oil flows well even in very cold conditions. A 5W is a step thicker in the cold but still performs well through most winter conditions in a temperate climate. A 10W is thicker still at startup, which matters more in genuinely cold climates than in milder ones.
The Second Number: Hot Weather Performance
The number after the W describes the oil's viscosity once the engine is at normal operating temperature, tested at 100 degrees Celsius. A higher number means the oil stays thicker once hot, which helps it maintain a protective film between components under load and heat. This is the number that matters most once the engine has fully warmed up and is working hard.
Why Multigrade Oil Exists at All
Older single-grade oils only performed well across a narrow temperature range. Multigrade oils, the 5W-30 style formulations used in nearly all modern vehicles, use additives that let the same oil flow well when cold and still protect well when hot, covering both ends of the temperature range with one product instead of needing to switch oils seasonally.
Why the Right Grade Actually Matters
Modern engines are built with specific internal tolerances designed around a particular viscosity range. Using an oil that's thicker or thinner than what your manufacturer specifies can affect how well oil reaches tight spaces inside the engine, and it can measurably affect fuel economy too. Your owner's manual lists the exact grade your engine is designed for, and that's the number worth following rather than a generic assumption.
Why Central New York Winters Make This More Relevant
Cold starts are genuinely harder on an engine, and the oil's cold-flow behavior matters more here than it would in a consistently mild climate. If your vehicle allows a choice between a couple of acceptable grades, leaning toward the one with better cold flow can make a real difference on a January morning.
Why Sholar Automotive for Your Oil Change
We use the exact grade your vehicle's manufacturer specifies, not a generic one-size-fits-all oil. It's a small detail that actually affects how well your engine is protected. Visit our oil change service page for more.
Not sure what oil grade your vehicle actually needs? Give us a call at (315) 252-7223 or schedule online, and we'll make sure you're getting the right one.