engine oils on shelf

5W30 vs 10W30 Oil: What’s the Difference?

Choosing the right engine oil is important if you want to get the most out of your vehicle (or generator), extend its lifespan, and save yourself some money. The problem is that things can get a little bit confusing – and especially when you head down to your local garage only to find that they have a random selection of oils available!

In this post, we’re going to take a look at two commonly used engine oils to uncover the difference: 5W-30 vs 10W-30.

Here is a short answer on what is the difference between these 2 oils:

  • 5W30 – This oil is more “fluid” at lower temperatures, making the process of starting your cold engine much easier. It is recommended for use at -35°C up to +35°C (outside temperature). It is more fuel-efficient as well.
  • 10W30 – While still quite “fluid”, this oil is a little bit thicker at low temperatures than 5W30, making the process of starting your engine a little bit harder. It is recommended for use at -25°C up to +35°C (outside temperature). It is thicker, less fuel-efficient and provides better sealing action.

After reading this, you’ll have a better understanding of how to choose between oils in general, and what all those letters and numbers mean for your vehicle!

5W30 vs 10W30

What do theSE Numbers Mean


The first sequence of numbers (before W) refers to the viscosity of the oil at low temperatures. 


The letter W refers to the word “winter” & is used to differentiate the oil’s viscosity at cold & hot temperatures. 


The second sequence of numbers (after W) refers to the viscosity of the oil at high temperatures (100 °C). 

Ever wondered what the difference is between 5W30 and 10W30 oil? Essentially, this comes down to viscosity – which is the technical term for thickness. If 5W30 is soup, then 10W30 is that same soup with a bunch of thickening granules stirred in!

Actually, the technical explanation of what this means in real terms, is that viscosity tells you how easy it is to pour the oil at low temperatures. In other words, a nice thin oil will run like thick water, whereas something much thicker will gloop and stick to a spoon.

The lower the number, the more fluid the oil will be. 

So a 0 will pour far more easily than a 5, and a 5 will pour more easily than a 10.

What does this mean inside the car? It tells you just how quickly the oil will reach the engine and internal components. Think of thick honey running through pipes versus running water – the water is, of course, going to travel around much more quickly.

So that explains the first number.

What about the second number, the 30? That tells you how thick the oil will be once it reaches higher temperatures or “operating temperatures.” In other words, heat causes the chemical composition of the oil to change, which in turn alters how it moves and travels. This is important, seeing as the engine of your car will be hot when in use.

This increased viscosity also means that the oil will become more sticky and therefore adhere to mechanical components better and lubricate them better. This becomes even truer, as the amount of pressure and stress on the system increases.

The higher that second number, the better the oil can withstand high temperatures before it starts to thin out and become less useful. When oil becomes too thin, it can no longer offer benefit to your engine, as it will just “run-off” the components.

When Should You Use

10W30 & 5W30?

When deciding which oil you should use, you should consider how quickly it flows. Remember: 10W30 is thicker when cool, meaning that it will move more slowly than 5W30 when you first start up your engine for the first time that day. Seeing as both these types of oil actually have the same viscosity, that means that the oil will perform the precise same way once it reaches operating temperature.

For that reason then, where circumstances are otherwise the same, 5W30 oil will help your car start up faster.

That said, if the oil viscosity is too low, this can cause it to fly off the engine components and thereby allow metal-to-metal contact, reducing the lifespan of your engine. If you want to do the very best you can in order to extend the lifespan of your vehicle, choosing the oil with the thickest viscosity will always be the smartest choice.

But there are caveats. 5W30 might be a better choice during very cold months. Warmer regions are safer to use the thicker 10W30. And if it gets even higher, then you can consider using something like 15W40.

Just take a look at the following table to get a clearer picture on which oil you should use when it is cold outside and which one is better to use on warm summer days:

What you might not realize, is that the “W” here actually stands for “Winter.” Oil that has a thinner viscosity when cold is better suited to use in low temperatures.

That said, most car manufacturers will provide information regarding the best type of oil to use, and these will let you know the range that is safe for you to put into your engine. This will not only ensure that the car gets the best protection for long-term performance, but should also optimize for the fuel economy ensuring that you can go further before running low.

Always use the weight of oil that is recommended, and you will have few issues.

Mineral vs Synthetic

What's the difference

Another consideration when choosing your oil is whether to use synthetic oil or regular motor oil. So what is the difference here?

Mineral oil is also sometimes referred to as “conventional oil.” This is the way oil has been made for a long time, and is produced by using natural resources (crude oil, which is made from minerals.)

Synthetic oil works slightly differently however. This is made artificially using chemical compounds – though in some cases a conventional crude oil may be used first as a base.

Synthetic oils therefore contain a number of additives and chemicals that make it distinct from regular oil. The types of these additives and their quantities however, are what ultimately determine how it performs. For instance, conditioners can be used in order to support the neoprene oil seals.

What’s more, is that synthetic oils can help to prevent freezing, while also maintaining the chemical structure of the oil at higher temperatures. In other words, synthetic oil does good for your engine!

You will still find that synthetic oil is graded in the same way, so you still need to consider the temperatures and manufacturers recommendations. Note as well, that synthetic oil is more expensive to purchase, but will typically last a lot longer. In some cases, synthetic oil may last 2-3 times longer than conventional oil, making it a savvy investment in the long run.

Some vehicles – such as Mercedes-Benz – specifically ask that drivers use synthetic oils. Again: follow the directions of your manual!

That said, if your car doesn’t specifically state that you should use synthetic oil, then either type will work just fine.

Choosing the best oil for your generator?

Can You Mix 5W30 & 10W30 Oil?

Will It damage your engine?

One question many people have about car oil, is whether it is safe to mix different grades. The short answer is: yes! It will work just fine, and won’t cause any harm to your vehicle.

In fact, chances are that you already mix car oils regularly without realizing it. After all, when your engine oil is running low, you don’t wait for it to become completely empty before filling it up! Even if you did, the old oil would still be coating the internal mechanisms of your engine.

Seeing as the main difference between 5W30 and 10W30 is the viscosity, this will not cause any huge difference to your vehicle’s performance. One type will reach the engine slightly quicker, while the other type will become more viscous.

That said, you may find that this reduces the economy and longevity of your engine ever so slightly if you do it regularly: after all, you will be getting the downsides of both types of oil. You should also be wary about mixing synthetic and regular oil.

So limit the mixing to oil changes and emergencies – but don’t lose any sleep over it!


Hopefully, you now have a good idea of the difference between 5W30 and 10W30. These are very much interchangeable oil types, where the primary difference is the viscosity during cold weather and standard operation.

More viscosity is a good thing as it coats your car’s mechanical parts more thoroughly to aid lubrication and prevent metal-on-metal friction. When this number gets too low, it can prevent the parts from being properly coated: the oil may simply get propelled off the engine, leaving the parts effectively “naked.”

At the same time though, too much viscosity can cause your engine to experience drag. This can slow things down and may cause issues in the long term. Your car manual should let you know the best type of oil for your vehicle, and simply following those guidelines will usually ensure the best possible outcomes.

Then you need to choose between mineral and synthetic oil. 

Whereas mineral oil is natural and more affordable, synthetic oil benefits from additives designed to protect your engine and provide more chemical stability. On balance, synthetic oil is normally preferable and will let your vehicle run for much longer.

Ultimately though, 5W30 or 10W30 are fine in most cases, for most vehicles. Likewise, you’ll often find that using either mineral or synthetic oil is fine. You can even mix the two!

One of the biggest take homes is not to stress when choosing oil: and if there’s only one type available in your garage, either will usually work well. Check the book that came with your vehicle, and you can’t go wrong.

Hopefully though, understanding the differences between these types of oil has helped you better understand your choices, and thereby buy with more confidence and awareness in future.

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About the author

Hands behind everything you see around. Matthew is the main workforce that puts all ideas into realization. So, do not feed him bad ideas.


handyman, loves science

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