Differences in 10w30 and 10w40 oil (& which is better?

The most popular engine oils are 10W30 & 10W40. Although they have some similarities in their nature, there are differences. Viscosity is what makes the difference between 10W30 and 10W40 oils.

Let us take a closer look at these different engine oils to help you choose the right one for your car. The oil viscosities are now clear.

Differences between 10W30 and 10W40

Quick answer: 10W40 at higher temperatures is thicker than 10W30. They have nearly identical characteristics. The only difference between the two is oil viscosity.

Sadly, that quick answer doesn’t make it any easier to understand. First, you will need to understand what oil viscosity and the meaning of numbers for both motor oils. 

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Understanding Oil Viscosity

Viscosity is a measurement of the thickness or consistency of liquids. Oil is thinner than water, for example. The water will flow more quickly if you pour oil and water at the same time. This is why oil has higher viscosity then water.

Many factors can affect viscosity, particularly when using different types of motor oil. Temperature is one such. You can make oil wax by putting it in the fridge for a few days. This is because oil viscosity, temperature and temperature are directly related. Oil viscosity drops as the temperature rises. When the temperature falls, oil viscosity rises. They are both proportional. 

Your car’s motor requires the right viscosity of oil to run correctly. It must adapt to different temperature conditions. Oil that is too hot can cause it to become too thin, which could result in damage to its inner parts. If the engine gets too cold, the oil may not flow as well. 

That’s where the oil grades come in. The oil grades are named according to their viscosity, and the way they will perform. 

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Understanding Oil Grade

Both oils begin with the number 10. The first number is used to indicate the oil's viscosity at low temperatures. This number is usually used for winter temperatures. It flows more easily in colder weather because the first number is lower. Oils whose numbers begin with 5 flow faster than oils with 10 designations. Winter stands for W, as you may expect. 

What does the second number on the oil grade mean? This number indicates how smoothly the oil flows at ideal engine temperatures, or in hotter months. This number indicates how much protection oil offers against extreme pressure and heat. 

Keep in mind that 10W30 and10W40 oil are identical except for the difference in viscosity when heated and under pressure. The viscosity of 10W40 will be thinner as temperatures rise.

What is the best time to use 10W30 oil?

10W30 is better for vehicles that live in cold climates. Motor oil only deals with heat from the engine and does not have to deal with additional stresses. The winter temperatures can be reduced by using 10W30 motor oils.

TenW30 is more commonly used than 10W40, as you will see. 10W30 is easier to locate and less expensive. 10W30 might be a better option if you're looking for an affordable solution. However, you don’t want to use it if you live in hot climates or it is the middle of a warm summer. 

How to Use 10W40 Ole Oil

10W40 is the best choice if your area has high temperatures all year. It’s designed to operate better at hotter temperatures and protects your engine from wear in the extremes. Not only will this oil handle the environmental heat better, but it’s also designed for engines that get hotter than others.

This means that you can still use 10W30 for warm weather but it will be thinner than 10W40. The temperature will continue to rise and it may not be able to lubricate all internal components. For better protection against high temperatures, you can spend more on 10W40 to be safer. 

Use 10W30 Motor Oils with 10W40

You will find many people who say mixing oils is fine if you do a search on the internet. It is not advised for multiple reasons.

First, mixing different motor oils can result in a lower oil pressure when the engine revs are higher. A bearing could become damaged due to this problem. 

Additionally, when you mix engine oils, you can void your vehicle’s warranty. Both oils work in cold conditions, but the thicker one will be more effective in warm climates. Unless there is an emergency, you don’t want to mix the oil grades and cause additional wear on your engine. Avoid this by always having your motor oil.