How to Pick the Right Motor Oil for Your Car

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There are many choices when it comes to picking the appropriate oil for your car’s engine. Our guide breaks down your choices to help you in the quest to change your oil.

Motor oil options are out there, choosing the right oil for your car might seem like an impossibly daunting task. While there is a mountain of info to learn about the various oil choices, the first step is honestly quite simple: Look in the owners manual, Contact Us, or call your local automotive parts store.

Your car’s owner’s manual will list the recommended oil weight, whether that’s a standard like 10W-30 or something more unusual. Later, we’ll explain what that weight means and how you should adjust it based on the seasons. But for now, choose an oil with the recommended weight from a brand that displays the starburst symbol that indicates the oil has been tested by the American Petroleum Institute (API). In addition, there’s a two-character service designation on the container. API’s latest service standard is “SL.” SL refers to a group of laboratory and engine tests, including the latest series for control of high-temperature deposits.

First lets take a look at an independent review of several motor oils 9 out of 10 times the proof is in the multimedia pudding.

Important Viscosity (thickness) that’s suitable for the “Heat” temperature range that your vehicle normally operates in.


Viscosity means a fluid’s resistance to flow. In motor oil, it’s rated at zero degrees Fahrenheit (represented by the number preceding the “W” [for winter]) and at 212 degrees (represented by the second number in the viscosity designation). Motor oil thins as it heats and thickens as it cools. So, with the right additives to help it resist thinning too much, an oil can be rated for one viscosity when cold, another when hot. The more resistant it is to thinning, the higher the second number (10W-40 versus 10W-30, for example), and that’s good. Within reason, thicker oil generally seals better and maintains a better film of lubrication between moving parts.

At the low-temperature end, oil has to be resistant to thickening so that it flows more easily to all the moving parts in your engine. Also, if the oil is too thick, the engine requires more energy to turn the crankshaft, which is partly submerged in a bath of oil. Excessive thickness can make it harder to start the engine, which reduces fuel economy. A 5W oil is typically what’s recommended for winter use. However, synthetic oils can be formulated to flow even more easily when cold, so they are able to pass tests that meet the 0W rating.

Once the engine is running, the oil heats up. The second number in the viscosity rating—the “40” in 10W-40, for example—tells you that the oil will stay thicker at high temperatures than one with a lower second number—the “30” in 10W-30, for example. What’s really important is that you use the oil viscosity your car’s owner’s manual recommends.

The Basic Function of Engine Oil

Without getting into the technical details, you need to know that at its most basic level engine oil is a lubricant. Its job is to make sure that the moving parts of your engine don’t rub together. If this were to happen, your car’s engine would stop working and your mechanic would either rebuild or replace your engine, depending on the damage done.

Explaning the Numbers

Two sets of numbers designate all motor oils sold today. The numbers are displayed as (Number) W (Number.)The first number is the oil’s cold viscosity rating and the second number is the oil’s hot viscosity rating. The “W” stands for winter and is the cold viscosity rating. This number tells you how easy the engine will start in cold weather. The lower this number, the easier the engine starts in cold weather.

5W-30 Pros and Cons

The pros of 5W-30: It is best for operating in cold climates, and it tends to give slightly better engine protection. The cons of 5W-30: It might not be suitable for vehicles that operate in hot climates, and it is not the best option for vehicles that are involved in frequent city driving (stop and go) or vehicles that frequently haul heavy loads.

10W-30 Pros and Cons

The pros of 10W-30: It is a better choice for vehicles that operate in hot climates; it is a better choice for stop-and-go driving; and it is a better choice for vehicles that frequently haul heavy loads. However, it is not as good as 5W-30 when used in extremely cold climates.




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