Choosing the right motor oil for your car can seem like a minefield. There are so many to choose from that you might be confused about where to start.
Using the wrong oil could lead to costly engine damage, but don’t panic. We’re going to cut through the confusion and help you make the right choice for your vehicle.
What is Motor Oil?
Motor oil is the lifeblood of your car’s engine. It pumps throughout the engine while it’s running via small passages called galleries.
Its purpose is to clean, lubricate, cool, and cushion moving engine parts. At the same time, it holds sludge, harsh chemical contaminants, and abrasive particles in suspension.
You must change your car’s motor oil regularly to keep your engine running smoothly.
Different Types of Motor Oil
What kind of oil does my car take? There are many types of motor oil available, which is where the confusion starts.
Motor oils are a combination of base oil and additives.
Base oils are derived from crude oil or natural gas. Typically, they make up 70% to 90% of engine oil. The remaining 10% to 30% are additives that perform specific functions. These functions include keeping the engine corrosion-free and optimizing oil consumption.
Here are the most common types available.
Conventional Motor Oil
Conventional motor oil is the least expensive type of motor oil. It starts as crude (base) oil. It then goes through a refining process that removes impurities and blends them with various chemical additives. Additives include:
- Detergents: to neutralize sludge
- Antioxidants: to inhibit metal degradation
- Antifoam agents: to prevent air bubbles
High-Mileage Motor Oil
This type of motor oil is specially formulated for vehicles with 75,000 miles or more on the odometer. The additives and enhancers contained in the oil cause the internal and external gaskets and O-rings to swell. When this happens, it potentially reduces oil leaks and oil burning in older engines.
High-mileage motor oil is not a solution if your vehicle has mechanical issues or excessive wear. However, it might be the right choice if you’ve properly maintained your vehicle and it runs and performs well. Potentially, it could extend the life of the engine’s critical parts and keep it running longer than planned.
Full Synthetic Motor Oil
Full synthetic oil starts with a base oil. In this case, more extensive refining processes remove more of the impurities. Higher-performing additives and artificially made compounds keep the engine cleaner and better protect it from damage.
Synthetic oil is superior, however, it’s not suitable for all vehicles. Older vehicle models tend to be better suited to conventional oils.
This kind of oil is the most expensive type you can buy.
Synthetic-Blend Motor Oil
Synthetic-blend motor oil is a mix of conventional and synthetic base oils and is the best of both worlds. It contains additives found in both.
The engine protection properties are excellent, but the cost is lower than full synthetics, typically around the middle price range.
Can Different Types of Oil be Mixed?
It’s possible to mix different types of oil, but it’s a waste of money. For example, if you add the more expensive full synthetic oil to conventional oil, you end up with the properties of conventional oil.
Synthetic blends are specially formulated with different additives. These better protect your car’s engine against high heat, cold weather, wear, and a build-up of sludge.
When you find yourself asking the question “what engine oil does my car take?” think about the type of driving you do. Your motor oil has to work harder and be changed more frequently when the driving conditions are harsh. Examples include off-roading, driving along dusty/dirty roads, and city vs. highway driving.
The most severe driving conditions take place during short trips of less than 15 minutes. If you don’t drive your car long enough for it to reach top operating temperatures consistently, water condensation won’t burn off and sludge will build up in your engine.
Different Oil Additives – What They Do
Oil companies generally use additives to improve and maintain oil performance. They help maintain good lubrication by minimizing sludge and varnish. Sludge and varnish are a problem when high engine temperatures combine with combustion byproducts such as unburned gasoline, moisture, corrosion, rust, oxygen, and engine-wear particles.
The main categories of additives include the following:
- Detergents: Detergents remove mostly solids. However, their main purpose is to keep surfaces clean. They do this by inhibiting the formation of rust, corrosion, and high-temperature deposits.
- Antioxidants: The result of tighter emissions regulations is higher engine temperatures. Antioxidants prevent oxidation that thickens the oil.
- Viscosity-index improvers: These improvers reduce the tendency of the oil to thin when the temperature increases.
- Dispersants: Dispersants disperse solid particles. They keep them in a solution that stops them from coming together and forming varnish, acids, or sludge.
- Friction modifiers: Friction modifiers reduce engine friction and improve fuel economy. Common compounds used for this include graphite and molybdenum.
- Anti wear agents: Antiwear agents protect the metal surfaces of your car’s engine because sometimes, the lubricating film created by the oil breaks down. A common agent is a zinc and phosphorus compound called ZDDP together with other phosphorus and sulfur compounds.
- Pour-point depressants: Oil doesn’t necessarily flow readily at low temperatures, even when the viscosity rating is low. The oil contains wax particles that tend to congeal and reduce flow. Therefore, additives will keep the oil flowing even when it’s cold.
- Rust or corrosion inhibitors: These inhibitors protect the engine’s metal parts from moisture and acids.
- Foam inhibitors: When motor oil is whipped by the crankshaft in the oil pan it can foam which reduces the lubricant effect. To stop foaming, oils have foam inhibitors which cause the bubbles to collapse.
What If Mixing Different Oils is Unavoidable?
In certain situations, mixing different oils may be unavoidable, for example, if you can’t find the engine oil you need.
When this happens, you should do the following:
- Choose an oil from the same manufacturer as the oil currently in your car. If that’s not possible, choose one with the same API Donut certification (you’ll find an explanation below).
- Choose a product with similar performance and chemical characteristics as the oil in your vehicle’s engine.
What Type of Oil Does My Car Take?
When choosing an oil for your engine, the most important consideration is the viscosity of the oil. It’s usually written in a format like 5W-30. The best place to look is in the vehicle’s owner’s manual.
In the owner’s manual you’ll find the following information:
- The engine oil viscosity and type recommended by the vehicle’s manufacturer
- Details for hot or cold climate use
- Alternative-weight oils you could use if you can’t get a hold of the exact recommendation
Not everyone has access to the owner’s manual, but don’t panic. There are other places you can look.
- The engine’s oil filler cap may list the viscosity rating
- You may find a small decal under the hood that the car manufacturer has applied
- Your car dealership may be able to give an engine oil recommendation
- The oil section in your local parts store may have a chart listing vehicle makes and models and the right type of oil to use
- Oil companies sometimes publish online databases where you can search for the information you need
- If all else fails, try checking with a professional mechanic
Check the Labels
Reputable engine oils have an API (American Petroleum Institute) donut and the API starburst symbols on the bottle (see above).
The API donut displays the following information:
- The SAE viscosity rating, for example, 5W-30, 0W-20
- A service designation on the container, for example, SP, CK-4, SN
- An indication that the oil has passed the Resource Conserving Test
The API’s latest service standards are:
- SP for gasoline (petrol) engines
- CK-4 for diesel engines
If you own an older car, it’s perfectly fine to use motor oil with an API service rating of SG. Newer cars may need SP.
The API starburst symbol shows that the engine oil has passed the service tests listed in the API donut. An oil that states it meets an API service standard isn’t the same as the one that’s been registered and tested for compliance.
What Does Viscosity Mean?
Viscosity is a term used to describe a fluid’s resistance to flow. In the case of motor oil, viscosity is rated based on how thick the oil is at zero degrees Fahrenheit.
The rating will have a number preceding a W which stands for winter and a second number after a dash which is the thickness of the oil at 212 degrees. For example, 5W-30.
At motor oil heats up it gets thinner and runnier. When it cools, it thickens. The thicker the oil, the better film of lubrication between moving parts and seals in your car’s engine.
When motor oil contains the right combination of additives, it stops the oil from thinning too much when it heats up. The more resistant the oil is to thinning, the higher the second number.
As well as being resistant to thinning when heated up, the oil must also be resistant to excessive thickening in low temperatures. Excessive thickening means the oil will struggle to flow properly to all your engine’s moving parts. Issues include difficulty starting the engine which reduces fuel economy. When the engine oil is too thick, more energy is required to turn the crankshaft which is partly submerged in oil.
For cold weather performance, a lower number is better before the W. For winter use, a 5W oil is typically recommended.
Once an engine is running and the oil has heated up, a higher second number is important for extreme uses and hotter running, more complicated engines.
Tips on Choosing the Right Motor Oil
There are several elements to consider when selecting your engine oil.
Engine Oil Viscosity
The viscosity of the engine oil is the most crucial factor. Viscosity, also known as oil weight, represents the oil’s ability to flow at various temperatures.
When engine oil heats up it becomes thinner. When it cools it thickens.
The thicker the oil, the better lubrication film it provides between the engine’s moving parts. However, if the oil is too thick, it could make it difficult to crank the engine. The engine requires more energy to move its parts, which reduces fuel economy.
Thinner oil, on the other hand, may flow better, but it might not offer sufficient protection for the engine’s vital moving parts.
Motor oil manufacturers commonly use additives to reduce the oil’s tendency to thin or thicken depending on the temperature. Additives also perform a variety of other functions that have already been discussed.
Climate and Seasons
Modern engine oils can perform at a range of operating temperatures. However, there are certain times when a specific oil grade will perform better.
If you live somewhere that experiences high temperatures, you should use an oil that is resistant to excessive thinning, such as a 10W-40.
If you live somewhere that experiences low temperatures, an oil that is resistant to excessive thickening might be better. A 5W-30 may be the best option.
There’s also a chance that you might need to change your engine oil from summer to winter if the extremes are wide-ranging.
Driving Conditions and Habits
If you regularly drive off-road or tow other vehicles, your engine will need motor oil that can work harder. More frequent oil changes may also be required. An oil with additives that help reduce engine friction under heavy loads and high temperatures might also be recommended.
If you regularly use your car for short trips of less than 15 minutes, it doesn’t allow your engine to reach optimum operating temperature consistently. This means water condensation won’t evaporate and will result in a build-up of sludge. In such cases, you need engine oil with additives that reduce or prevent sludge formation.
The Age of the Engine
A new car that has a high-rev engine and multi-valves typically requires a thinner oil to help reduce start-up damage. On the other hand, an older engine likely needs a thicker oil for correct oil pressure between the worn engine parts.
Final Thoughts
As you can see, answering the question “What type of oil does my car take?” is not straightforward.
Now you’ve reached the end of the post you’ve got all the information you need to make a decision that’s best for your car and its engine.