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Oil Weight Explained: What Does It Mean & How To Read
Motor oil lubricates critical engine components, reducing wear while improving efficiency. To fill your vehicle with the correct type, you must know the exact oil weight specified by the manufacturer. The proper oil weight is vital to an engine’s daily performance and longevity.
Use the guide below to discover what oil weight means and how to read oil labels to find the appropriate oil weight for your vehicle. Understanding the link between oil viscosity and performance enables you to match the proper oil weight to what your vehicle’s manufacturer recommends.
Trust the experts at Cadence to supply you with high-quality motor oils across a variety of oil weights and types.
What Is Oil Weight?
The term “oil weight” describes how well motor oil flows and protects internal machinery or engine components at varying temperatures.
The Society of Automotive Engineers (SAE) classifies oil based on its viscosity. The resulting oil weight — also known as oil viscosity — indicates how well the lubricant performs at both cold and hot temperature extremes.
Motor oil weight directly impacts an engine’s performance and longevity. The more viscous oil is, the better it performs at high temperatures, but the harder it is to turn over the engine in the cold. Conversely, low-viscosity oil is better for cold start-ups, but it breaks down much faster at higher operating temperatures.
Oil viscosity can also vary between synthetic blend, full synthetic, and conventional oils. Compared to synthetic oil, conventional oil has a lower viscosity, which means it’s less stable at higher temperatures and has a shorter service life. Conventional oils also rely on additives like viscosity modifiers to improve their lubricating properties.
Full synthetic oils tend to be more stable and have higher viscosities at startup, which helps boost fuel economy and reduce engine wear. Synthetic blends are somewhere between conventional and full synthetic oils in terms of viscosity.
How To Read Oil Weight
If you’ve ever looked at a display of motor oil and been overwhelmed by the sheer number of available options, you’re not alone.
No, the “W” on most oil labels doesn’t stand for “weight.” However, understanding the concept of oil weight can help you determine what numbers like “0W-40,” “5W-30,” and “10W-40” mean so you can more easily locate the appropriate oil weight your car requires.
The “W” in the oil weights listed previously stands for “winter,” indicating the oil’s particular viscosity in cold, icy temperatures. The reason you see a number before and after the “W” is because that particular oil is considered multi-grade, which means it performs across a wide range of temperatures, from hot to cold.
Motor oil with a lower “W” rating (5W-30 compared to 15W-30, for example) tends to be less viscous in colder temperatures. It flows through the engine quicker than a more viscous oil (i.e., 5W-40 versus 5W-20) that performs better at higher temperatures.
Vehicle manufacturers will call for various oil weights depending on the corresponding engine requirements.
How to Choose the Best Oil Weight for Your Vehicle
The best oil weight for your vehicle can vary from the oil weight an owner of the same car runs in another climate. Driving habits and application also impact which oil weight best suits your vehicle.
Due to their tighter tolerances, newer vehicles often call for lower oil weights than older engines, which tend to perform better with thicker, heavier oil.
When selecting the best oil weight for your vehicle, start with the owner’s manual. Some owner’s manuals list a range of acceptable oil weights, while others only list a single weight. When manufacturers recommend multiple weights, drivers have the option to tailor their chosen oil weight to their climate, driving habits, and application.
For example, thinner oil weights are ideal for cold startups and city driving. Thicker oil weights do better in hotter climates, especially when tropical temperatures last through most of the year. If you often tow heavy loads, a thicker oil can help reduce the strain on your car’s engine.
It’s also important to pay attention to the additives that influence an oil’s performance regardless of weight. Oil additives, such as detergents, anti-wear agents, and viscosity modifiers, are designed to reduce friction, improve performance, and increase longevity.
How Does Oil Weight Impact Oil Change Intervals?
Oil weight can certainly impact the life of your vehicle's oil. Thicker oil tends to last longer at higher operating temperatures but can fail to offer the same protection as thinner oil at lower temperatures. Lower-weight oil also flows better at startup but breaks down quickly under heavy loads.
The type of oil you use can also significantly impact your oil change intervals. Follow the manufacturer’s recommendations for conventional vs. synthetic use and routine oil change intervals. You can also tailor oil changes to your driving habits, climate, and operating conditions.
Can You Switch Between Oil Weights?
Mixing oil weights is never a good idea. However, you can switch between oil weights if you do so with care. It’s best to follow the owner’s manual, but when those recommendations include a range, your options multiply.
If your engine is high-mileage, you tow or drive aggressively, or you experience distinct seasonal changes in the climate you live in, switching between oil weights makes sense. You can run different oil weights in the summer and winter to accommodate the average temperature. Thicker oils can protect high-mileage, work-horse engines that perform to higher standards.
Cadence: Your Source for High-Quality Lubricants
Oils of the same weight aren’t necessarily made to similar specifications. Discover the difference high-quality lubricants can make in seamlessly maintaining your vehicle or fleet, reducing downtime, and improving performance. Call us at 336-629-2061 to speak with a friendly and knowledgeable representative about how Cadence can deliver value to you.
Sources:
Motor Oil | Hall County, GA - Official Website
Conventional Oil — Sources — Student Energy | Student Energy
(PDF) Review of Viscosity Modifier Lubricant Additives | ResearchGate