Can You Mix 5W30 And 5W40

Engine oil must be added to internal combustion engines regularly before you see the low oil volume warning light, although many people accidentally top up oil when they see this.  Engine oil lubricates and protects engines against seizing by keeping all parts lubricated and protecting the parts against high temperatures.

Various engines use different oil weights, depending on the type of engine. However, if you can’t get the right one for your engine, it could leave you stumped. Some engines use 5W-40 oil, while others use 5W-30 oil most often. So, you may be left with the question if, in the middle of nowhere, can you mix 5w30 and 5w40 together without harming your engine?

The two oils are miscible, so that they will mix into one solution; besides, you can use different engine oil, although it is recommended, they are all the same brand.  When you need to know about mixing oils, there can be a little more behind the answer, so here, you can find out more. (Learn How Does A Drive Shaft Break)

engine oil

Not only will you find out can you mix 5w30 and 5w40 oil types together, but also the answer to “can I use 5W40 instead of 5W30 oil if the worst scenario arises?”

Can I Mix 5w30 With 5w40 BMW?

Mixing 5W30 and 5W40 is possible without causing damage to your engine.

You haven’t yet determined if you should mix these oils in your engine. However, it is not advisable to regularly mix 5W30 and 5W-40 in your engine.

If you’re low on engine oil and can’t find locally the same weight, using a 5W-30 viscosity rating instead of 5W-40 is preferable to going without.

It should be fine to mix engine oils as long as they are from the same manufacturer.

The problem with mixing different oils of engine oil is that the properties of the mix are unknown.

As a result, if you continue to mix oils or use improper engine oil for an extended period, this could cause problems in your engine.

Engine oils are manufactured to a specified weight and viscosity specification.

The viscosity of a liquid determines how thick it is and how well it resists deformation. As a result, mixing the oils may alter the properties of the oil, perhaps causing unforeseeable adverse side effects.

How Do 5W-30 AND 5W-40 Differ?

You can buy many types of engine oils, and if you don’t know the difference between 5w30 and 5w40, it can be not very clear. Reading the car manual helps find the right type, yet the owner’s manual won’t tell you why and what the full benefits of using that oil are.

The difference between 5W-30 and 5W-40 is how they function at higher temperatures.

5W-40 outperforms 5W-30 in hot weather, making it perfect for high temperatures.

Breaking down 5W40 vs. 5W30 names offers some insights. First, both have a “W” and start with a 5.

The last values in 5W-30 and 5W-40 denote viscosity when it faces high heat. You should note that using the correct viscosity of engine oil is crucial. (Read Cleaning Battery Cables Guide)

If your engine oil is overly viscous, it will harm performance as it flows through the engine. Low-viscosity rating oil improves performance, although it doesn’t protect engine parts.

For example, Valvoline Full Synthetic SAE 5W-30 Motor Oil is suited to cold and warm regions and offers efficient performance and wear protection.

Another oil is Castrol EDGE 5W-40 Motor Oil, a fully synthetic, warm-and-cold-weather oil which is also a popular choice.

oil in winter

Which Oil Is Best For Winter?

Should you use 5W-30 in the winter when 5W-40 is preferable for summer in hot climates?

Both 5W-30 and 5W40 oil are suitable for lower temperatures; therefore, neither is better.

The “5W” at the start of their names means that they have the same viscosity at low temperatures and are hence winter-suited engine oils for cold climates.

Both engine oils have a low 5 cold-weather viscosity.

The “W” means winter, and the number means how effectively it flows in the winter. A low number means it will flow evenly.

10 or 15-grade engine oil performs poorly at low temperatures, unlike 5-grade oil.

The first number shows performance at low temperatures, whereas the last number shows performance at high temperatures. So, climate can affect which engine oil is ideal for your car.

What Oil Can You Mix With 5W30?

Engine oils may be labeled with different numbers and letters, such as 5w30 or 5w40. These codes are the grade of engine oil, or viscosity grade, which is based on the viscosity of the engine oil.

Different engines use only oil rated for them, yet you’ll find many different oil grades.

High-performance engines with high operating temperatures use thicker oils as once the oil thins; it doesn’t offer as much protection as it is still thick.

Less viscosity means less ability to lubricate components.

Because the crankshaft is partially buried in oil, thick engine oil can cause difficulty starting the engine at low temperatures, and it could affect fuel economy if the engine struggles.

Newer synthetic oils flow evenly in low temperatures, so these can handle severe operating temperature changes.

Can you mix 5w30 and 5w40?

Most cars use manufacturer-recommended oil, which varies based on a few things.


5w40 performs better in hotter climates, so it is recommended for cars in these regions.

Engine type

Cars with turbo’s run at higher temperatures, so use 5w40 oils, which are more effective at higher temperatures than 5w30.

Type of vehicle

Heavy-Duty vehicles like pickups use viscous oil since diesel engines have a higher compression ratio than gasoline engines.

As engines age, they become less efficient, seals in the engine wear and often leak. However, some synthetic oils come with additives for older cars, which extend the life of seals and prevent leaks.

Neglecting oil changes leads to a buildup of sludge in the crankshaft. Often the sludge is removed during oil changes, but if your oil isn’t changed, this can cause engine problems because of lack of lubrication and engine seizes.

Refer to your car’s owner’s manual for the recommended oil grade. In addition, when purchasing engine oil, look for the SAE (Society of Automotive Engineers) viscosity rating to ensure you get the correct oil. (Read Is Power Steering Fluid Clear)

Is It OK To Mix Different Weights Of Motor Oil?

Are 5w30 And 5w40 The Same?

5w40 oil is more effective at higher temperatures, up to 50C, than 5w30 oil, which remains viscous at -30C.

Can You Mix Engine Oil Grades?

Mixing two oils with similar properties is possible but not guaranteed. There is no restriction on mixing market oils (petrol engines, diesel engines, mineral or synthetic oils). The superior quality is reduced by combining two oil qualities.

Can I Mix 5w40 oil Instead Of 5w30?

Mixing different viscosity oils, such as 5w30 and 5w40, is fine, especially if you’re low on oil, just as mixing full synthetic with semi-synthetic oil. Not ideal if you want the motor oil brand’s benefits.

harmed car

Will The Wrong Engine Oil Harm My Car?

If you’re low on engine oil, a mixture of 5w30 and 5w40 will do. It can offer proper viscosity and lubrication of components in the engine, even if it’s not optimal in a hot climate.

Motor oil formulations are exact. As a result, mixing oil weights may alter the ratio, resulting in an unstable or poorer product for your vehicle.

Mixing oils from different brands can be a bad idea as it could negatively impact the performance of the car’s engine in a couple of ways.


Each motor oil brand has different additives. Additives maintain engine cleanliness, viscosity, and efficiency.

Mixing brands of motor oils changes some of these properties, causing severe harm to car engine performance.

Oil Stability:

A mixture of different weight oils won’t offer the advertised viscosity. Mixing purposely and in a ratio (50/50) creates a viscosity in between that is too thin or too thick to lubricate your parts efficiently.

Engine oil is an essential part of vehicle maintenance. If you want to add one weight of oil to another when running low, use the same motor oil brand, which ensures no oil additives change and they provide proper viscosity and optimum ratio for your car engine.

Can I Mix Synthetic Oil and Conventional Oil?

You can choose synthetic or conventional engine oil for your car. In terms of protection and lubrication, synthetic oils typically outperform conventional engine oils. But is it safe to mix synthetic and conventional oils in your engine?

Synthetic and conventional engine oils can be mixed without damage. However, the mixture will perform worse than synthetic motor oil alone.

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