Can You Mix 5W30 and 10W30 Engine Oils?

Oil is one thing an engine can’t do without. Its main purpose is to lubricate metal parts so that there is little or no friction which will cause them to wear out as they are put to use.

It’s a viscous liquid, meaning it has sufficient thickness and resistance to flow. Oils are classified according to their viscosity. For example, we have 5W30, 10W30, 5W20, etcetera.

Engine oil requires being change from time to time depending on your car’s mileage or when last you changed it. Usually, it’s recommended you change your engine oil after three months or covering a distance of 5,000 to 7,500 miles. Whichever comes first, your oil should be due for change. However, these isn’t all the factors to consider when planning for oil change.

Many times, we find ourselves in a situation where we can’t readily find the exact oil specification for our engine and we are forced to consider something else.

To this end, this article explores the possibility of mixing the 5W30 with 10W30 oil or adding the 5W30 to the 10W30 oil.

Can You Mix 5W30 with 10W30?

The answer one would likely get is ‘Yes, you can mix 5W30 and 10W30 engine oil.’ However, such action is not recommended because of their difference in viscosity. It is seen to be quite commonplace among many car drivers although without significant complaints. In other words, drivers are saying that mixing the two oils did not cause harm to their engines.

The 5W30 and 10W30 oils are both commendable for performance and viscosity. These oils are almost the same. The main difference between the two oils is the cold-flow. Otherwise, they have similar properties. You can mix the 5W30 and 10W30 engine oils, but only when the two oils are at operating temperature.

At operating temperature, the 5W30 and 10W30 oils are the same and can be mixed, but at low temperatures, they show different reactions. Therefore, they can’t blend during cold temperatures.

Keep in mind that you can’t mix the oils which come with the same weight. This is the reason why 5W30 and 10W30 might not go down well in blends as the two oils have the same weight. By the way, viscosity should not be confused with weight.

At cold temperatures, the 5W30 oil is thinner while 10W30 becomes thicker. It is worthy of note that engine oil has different additives within them, with different viscosities as has been stated earlier. Therefore, mixing two oils will not blend the oils.

Can you add 5W30 to 10W30?

Yes, you can add 5W30 to your 10W30 to make up. Although the new oil coming in means the current oil is already burning. No severe damages are likely to occur. In terms of operating temperature, the two oils are practically the same.

We can also state the aforementioned for the case of adding 10W30 to 5W30 oils. It causes no harm to your engine though it isn’t advisable to do so.

Is It Bad to Mix Two Different Engine Oils?

If you mix different types of oils, you run a risk of destabilizing your motor oil, reducing its efficiency which ultimately would affect the performance of your engine. The best choice would be to maintain the oil type and oil change intervals recommended by your car’s manufacturer and consult your local care experts for affordable services.

Can Synthetic Oil Be Mixed with Regular Oil?

Yes, you can mix synthetic and regular oil. There is no risk involved. But it can be noted that conventional oils tend to beat down the quality performance of synthetic oils and reduce the benefits while causing no harm to your engine.

Can You Mix Different Synthetic Oils?

Let’s take two brands of oil for example, Mobil and Amsoil. You can go ahead to mix the two brands of oils. You can also have a blend of conventional oil with synthetic oil. They can be safely mixed without any fear of damage.

However, using one type of oil on your engine rewards you with extra advantages over blends or changing between types of oil.

What Do Oil Viscosity Numbers Mean?

The numbers are referring to the oil’s measure of viscosity, or the thickness of a fluid (it doesn’t refer to how heavy an oil is). The higher the number the thicker the oil. However, the numbers also depend on temperature. A 10W30 rating means the oil has a viscosity grade of 10 in cold temperatures and 30 in warm temperatures (“W” stands for winter).

This doesn’t necessarily mean that the oil picks up more viscosity as it heats up, it’s simply telling that the oil will act like a 10-weight oil when it’s cold and a 30-weight oil when it’s hot.

In general, oil viscosity actually decreases as it heats up. Talking about viscosity, where this is very important is in an engine’s bearing clearances.

Engines that are older being built with much more relaxed tolerances allowed oils such as 10W30 to be commonly used as an original equipment (OE) recommended oil during the 1990s and before. More newer engines being built with better technology and much more strict tolerances call for the necessary use of thinner oil to properly lubricate the engine’s bearings and circulate faster with easier flow throughout the engine, oftentimes with less overall oil in the system.

Viscosity will determine how your engine’s oil will deal with temperature changes, pressure and speed. What is advised is that you follow recommendations from manufacturers for oil viscosity.

Differences Between 5W30 And 10W30

Apart from their weight and temperature these two oils have reasons which make one different from the other.

For 5W30 Oil

  • The 5W30 is thinner than the 10W30.
  • This oil is used for light-duty engines.
  • 5W30 is thinner in low temperatures.
  • This oil lacks the capability to provide sealing activities.
  • Gives service within the temperature of 30 to 35 degree Celsius.
  • Can be used with the help of light service petrol and diesel.

For 10W30 Oil

  • The 10W30 is thicker than 5W30.
  • 10W30 is used for heavy-duty engines that have to carry heavy loads.
  • You will notice it’s thicker at low temperatures.
  • This oil is highly capable of providing sealing activities.
  • Provides services within 18 to 30 degrees Celsius.
  • Requires heavy load-hauling engines.

Which Has a Better Performance: 5W30 or 10W30

It all depends on the engine requirements and the climate around you. How these oils work to serve engines are not the same. You can’t use both on the same engine. You have to determine which is best fitted for your engine according to manufacturer’s recommendations.

5W30 is well suited for engines which do not do heavy work like carrying heavy loads. It is thinner and becomes more and more thinner during cold temperatures. It can’t be used for sealant purposes. So, it’s safe to say it’s good for light-duty engines.

10W30 is the oil highly recommended for heavy-duty engines. Opposed to 5W30, it is thicker at low temperatures. With its features, it is very good for heavy-duty performance.

It all boils down to choosing the right oil for your engine for optimal results.

When Should one Switch from 5W30 to 10W30?

Both oils are the same at operating temperature. But when the temperature drops 5W30 becomes thinner and 10W30 thickens up.

If you are based where it’s cold most of the time then the 5W30 oil will be a good choice for you, especially during the winter period. And when it becomes hotter 10W30 can be the preferred choice. With considerations on whether it’s a light-duty or heavy-duty service.


It is best to stick with one type of oil. But in a case where there aren’t other options the oils can be mixed without any fear of damage to the engine. Although the mixture won’t yield optimal result as compared to using a single type that’s recommended for the engine.

Leave a Reply

Your email address will not be published. Required fields are marked *