Your vehicle’s motor oil is among its most vital and important components—lubricating, cooling, and protecting the heart of one of the biggest investments you can make.
Many mechanics refer to motor oil as the “life blood” of your vehicle, and that’s no exaggeration. The quality of your motor oil not only helps protect the intricate metal parts of your engine from overheating on long summer drives at high speeds, but it also forms a protective layer that keeps those same delicate parts from colliding and destroying themselves.
It’s important to note that motor oil needs to be replaced every 3,000 – 5,000 miles in most vehicles and not every vehicle engine takes the same type of oil. Developing a good understanding of what oil your vehicle needs and what the differences are between the oils on the market will help you be a more conscientious vehicle owner.
Oil service light on dashboard; Photo by vchalup/Stock.Adobe.com
WHAT IS "OIL WEIGHT" AND WHY IS IT IMPORTANT?
Each engine will require a motor oil that matches its performance needs and manufacturer specifications, allowing all your engine components to move freely with enough of a film of oil to protect them from heat and damage.
Viscosity, or a fluid’s resistance to flowing, is how the Society of Automotive Engineers (SAE) determines the “oil weight” stamped on the outside packaging of motor oils. The thicker or more viscous an oil is, the higher the numbers will be. The multiple oil weight numbers SAE assigns to most motor oils simply describe the oil’s viscosity at certain temperatures.
Variety of motor oils on store shelf; Photo credit Stock.Adobe.com
UNDERSTANDING HOW TO READ OIL WEIGHTS
Reading the weight of oil can be confusing if you don't know what you're looking at on the shelf. Every motor oil you see will have a weight rating clearly marked on the side of its bottle. It will be formatted and have numbers like this:
Oil weights are determined by their viscosity at low and high temperatures, the two predominant states of a vehicle's motor. Your oil's ability to flow when your vehicle has just started in the cold is the first weight number on the bottle, or the number with the W after it. The lower this number, the lower the viscosity and the faster the oil will flow when you first start up your vehicle's cold, resting engine.
The high temperature weight is the number appearing after the dash on the bottle. This number indicates the viscosity of the oil moving through your engine after it has warmed up and temperatures inside the motor have risen.
The lower the viscosity numbers you see on a motor oil, the more easily your engine components will move and the more improved your fuel economy will be. The trade-off of lower viscosity, however, is protection. The lower weight oil may flow more freely, but it also provides a thinner layer of protection between the delicate metal surfaces of your engine components.
Sometimes, you'll find single grade motor oils that only have a 0W, 5W, 10W, etc. rating. This rating is reserved for oils designed for winter applications where temperatures are consistently low or below freezing. Naturally, as temperatures drop and fluids solidify, your motor's oil will become thicker and more viscous. Lighter weight (less viscous) oils may be needed.
Customer deciding on which type of motor oil to buy; Photo by Igor Kardasov/Stock.Adobe.com
HOW MANY TYPES OF ENGINE OIL ARE THERE?
There are four basic oil types across the various weights of oil on the market today: synthetic oils, synthetic blends, conventional or regular oils, and high-mileage oil.
Synthetic Oil: These oils have been chemically engineered to create a more uniform molecule shape, reducing impurities and handling extreme heat and freezing cold temps better than conventional oils.
Conventional / Regular Oil: Conventional oils are formulated for older, less-complex engine designs and for drivers with a more relaxed driving style.
Synthetic Blend Oil: Synthetic blends use a mix of synthetic and conventional oil. This helps protect engines from oxidation as well as handling low temperatures better than conventional oil alone.
High-Mileage Oil: As engines age and progress past the 75,000 mark on the odometer, high-mileage oil may be preferable. Engineered with additional additives to fight oil burn-off and prevent gasket leaks, high-mileage oil can keep vehicles running longer.
Mother adding motor oil to car as son observes; Kyta Willets/Stock.Adobe.com
WHAT KIND OF OIL GOES IN MY CAR?
The easiest way to determine what oil weight your vehicle needs is by checking the oil cap under the hood. Usually this information is conspicuously displayed there, but if not, your vehicle’s owner’s manual will have the manufacturer’s recommended oil weight for your engine. It will also include more in-depth information on oil change intervals that will let you know how often your engine needs an oil change.
You should also consider the conditions you typically drive in as well as the climate where you live. The idea is that you want your oil weight to perform well in all temperatures, even extreme heat or cold, because it needs to maintain enough viscosity to lubricate components while also forming a protective layer that prevents those same metal components from rubbing and wearing out prematurely.