Car Care

10W30 vs. 10W40 Engine Oil: Which is Suitable for You?

10W30 vs. 10W40 Engine Oil

As your vehicle's engine is running, oil has to be pumped through to lubricate the different metal parts to minimize friction so that they function optimally. But as important as oil might be for the functioning of a vehicle, you cannot use just any as you need to pick the right one for your engine.

Two of the most common types of oils out there are 10W30 and 10W40, and despite both being quite popular, many motorists tend to have difficulties deciding which to use between the two.

What makes choosing between the two hard is often just a lack of understanding of what they are and what sets them apart. And while in reality there is no much difference between these two oils, it is still important to understand how they differ to ensure you make an informed pick.

What Do the Numbers Mean?

When it comes to choosing between 10W30 and 10W40, you should first start by comprehending what the numbers mean. If you know what the numbers mean, you will have a better understanding of the two oils, and so it becomes easier to choose.

The first number, which in this case is 10 for both oil types, indicates the ease of pouring the oils at low temperatures. Here, the smaller the number, the easier the oil will be to pour. Hence, an oil with a 5 will be easier to pour at lower temperatures than one with 10 like these two.

The W will stand for winter, and it is simply there to let oil users know that the first number is used to indicate the oil's cold temperature viscosity.

Because the last number is the only difference between these two oils, it is probably where you will need to pay more attention as it is what sets them apart.

Here 30 and 40 indicate the oil's ease of flow at the engine's optimal operating temperature. And the higher it is, the better the oil will be at lubricating the engine at high temperatures. Hence, 10W40 will be then better option for higher temperatures and warmer weather.

When to Use Which



Given the differences in viscosity, it should also be obvious that these oils will also work well for different situations. Hence, one of the best ways to choose between them is by understanding what each will be best for.

If you live in areas with cold weather, the 10W30 will be the more appropriate choice as here the only heat the oil has to endure is from the engine and not from the environment.

Motorists in hotter regions will need a thicker oil like 10W40 as the engines will be affected by both the heat that they produce and heat from the external environment. Using the 10W30 in such a situation can still be an option, but the problem here is that it will thin out easily given that it is already a thinner oil to start with.

If your oil thins out fast, it will not be able to provide effective lubrication to the engine parts which can in some instances lead to damages. At high temperatures, 10W40 not only provides superior lubrication but also protects the different metal components.

Fuel Economy

With the ever-increasing fuel costs, it is always important to try and get a few extra miles from your gas. The kind of oil that you use will affect your vehicle's gas consumption.

Between these two oil types, the 10W30 will offer much better fuel economy than 10W40. And if you also add the fact that it is a more common and widely available and hence a cheaper oil type, you will see that it will be generally more economical to use.

What makes 10W30 more fuel-efficient is the fact that it is thinner, and hence it will allow the engine components to move effortlessly and work less. This means there is less friction to work against, and so less fuel is used.

But, as an informed motorist, fuel economy should not be your top priority and should instead focus on getting oil that will ensure your engine runs smoothly and efficiently.


The choice between 10W30 and 10W40 should be a more straightforward one if you know the condition of your vehicle and also the typical environment that you will use it often.

While the difference between the two is not that great, understanding things like the viscosity will be vital in determining when and how to use these oils. And because each has its benefits and shortcomings, it is not accurate to say one will be better than the other as it largely varies from one vehicle to the other.

Overall the 10W30 will be the more appropriate oil for cold weather and non-performing engines while 10W40 is perfect for warmer temperatures and older vehicles. But, if you are still not sure what to use, talk to your local mechanic or check the vehicle's manual.


  1. 10w30 vs 10w40 Engine Oil – Mechanic Base
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