Can You Mix 5W30 and 10W30 Engine Oil?

Do you have some leftover 10W30 engine oil and plan to mix it with 5W30 to save some bucks? Will it be a good decision for your engine?

Can you mix 5W30 and 10W30? Yes, you can mix 5W30 and 10W30. But it isn’t ideal as both oils flow at different rates due to their different temperature endurance.

Basically, 5W30 grade engine oil performs well at low temperatures and 10W30 at medium temperatures. If you need to mix 5W30 and 10W30 in an emergency, use some additives and put the lighter one first.

Understanding Motor Oil Viscosity

To better understand motor oil viscosity and prevent engine damage, you must use the correct motor oil for your car.

Motor oil’s viscosity is determined by the thickness of its lubricant and how well it flows. 5W30 motor oil has a lower viscosity and flows better than 10W30 oil.

It might not seem important, but there are reasons for the different viscosities of 5W30 and 10W30.

What Does the Viscosity Code Mean?

The numbers and letters that makeup oil grades, such as 5W30 and 10W30, refer to the oil’s viscosity ratings, especially its temperature grade.

5W and 10W: The 5 or 10 before the ‘W,’ which stands for ‘winter,’ indicates the oil’s viscosity at low temperatures (i.e., cold weather performance). The lower the number, the thinner the oil at low temperatures, and the better it will flow.

5W: Thin oil (for cold conditions); the numeral stands for SAE ‘weight,’ which indicates consistency; the number is lower for thin oil. The first number matters more because the oil must flow better when the engine is cold at the start of a car.

10W: Thicker than 5W but still slides nicely in the cold.

30: The second number indicates the oil viscosity in the engine at its normal operating temperature. In 5W30 and 10W30, the ’30’ means that these oils will have similar characteristics when the engine is at optimum temperature and provide sufficient protection and lubrication at this stage.

Can You Mix 5W30 and 10W30?

If your car’s manufacturer recommends 10W30, you can mix 5W30 engine oil. In warm climates, the mixture of 5W30 and 10W30 will act quite similarly since both have the same viscosity at operating temperatures.

But if your car manufacturer recommends 5W30, this mixture won’t pump properly at very cold temperatures.

If you’ve already mixed 5W30 and 10W30 as an accident or as a result of outright ignorance, don’t worry. Your engine will survive till the next oil change.

However, mixing these two oils mightn’t get the desired output. 5W30 engine oil is lighter and has less density, while 10W30 is a higher grade and has more density.

One common purpose of planning to mix 5W30 and 10W30 is to get thicker oil. But mixing 5W30 and 10W30 will still provide you a 30 weight at operating temperature.

So, this experiment won’t be helpful. Instead, you can mix 10W40 with the 5W30 following a 50-50 ratio to get thicker oil.

Potential Consequences of Mixing 5W30 with 10W30 Engine Oil

Mixing 5W30 and 10W30 won’t hurt your vehicle immediately but can reduce the engine’s performance and shorten the oil changing interval.

The reason is that these oils have different additives which won’t let them blend properly. Using a mixture of 5W30 and 10W30 can also affect the proper flow during the cold season.

10W30 engine oil is also thicker than 5W30, making it better for carrying heavier loads and use during colder temperatures.

But in warmer climates, thinner oil like 5W30 is more beneficial as it can provide more lubrication. But mixing these two grades won’t let them do their job properly.

The 5W oil has a hydrocarbon molecular structure different from the 10W type. So if you mix 5W30 with 10W30 engine oil, it’ll cause out-gassing. The hydrogen’s out-gassing can dry out the engine’s valve seals and collapse the hydraulic lifters.

Warranty is another crucial consideration. If your car’s manufacturer suggests using only the 5W30, they’ll void the warranty if they notice different grade oil in the engine.

Can You Put 10W30 instead of 5W30?

If you add more viscosity oil than the recommended, nothing should happen to the engine. The crankcase’s engine oil won’t be affected.

However, replacing the recommended 5W30 with the 10W30 will reduce the engine’s longevity and increase the wear of some expensive components. This change will also slightly reduce the car’s miles per gallon performance.

Modern car engines are designed to accept particular lubricants. A modern engine with chain tensioners and a VVT system needs specific oil pressure to run properly.

5W30 engine oil is a good option for an area with 100F ambient temperature. Though 10W30 won’t cause any problem in 100F+ weather on a cold start, it won’t benefit the engine as well.

Instead, you can notice a bit of cam phaser noise in the car engine on cold starts, as 10W30 can take slightly longer to reach the engine’s top than 5W30.

If you accidentally put some 10W30 on an engine that suits 5W30, keep driving till the next oil change. In this case, you’ll have some quarts of 5W30 and a quart of 10W30 they never mix.

So, don’t use an oil with a different viscosity and stick to the oil the manufacturer specifies.

Difference Between 5W30 and 10W30

Below we’ve discussed some key differences between 5W30 and 10W30 engine oil to help you realize the effect of mixing or using one instead of the other:

1. Design Purpose

Both grades of oil are similar in terms of their second number. But the difference is in the first number before W. At below-freezing temperature, 5W30 engine oil will be thinner than 10W30 engine oil.

5W30 oil is intended to work effectively at 30 to 35°C. So, this oil is perfect for the area where temperatures rise too high in the summer and drop too low in the winter.

10W30 grade oil is designed to work effectively at 18 to 30°C in high temperatures.

2. Viscosity

10W30 is a higher viscosity oil and flows slower at low temperatures than 5W30. 10W30 engine oil provides the same protection as the 5W30 to the engine parts.

Both 5W30 and 10W30 engine oil have the same viscosity. But 5W20 and 5W30 engine oil have different viscosities.

Still, high-speed oil is a better sealant and offers more effective lubrication to the engine’s critical parts.

Conversely, more viscous oil forces the engine to work harder to complete the task and causes higher gasoline consumption.

3. Weather

Though multi-grade oils can act effectively in any climate, 5W30 engine oil is thinner, making it ideal for extremely low temperatures.

So, 5W30 oil will provide better performance during the winter season. It’ll flow properly even at -22°F temperatures.

10W30 flows more effectively in high temperatures, making it suitable for use during summer. 10W30 engine oil will work until 0°F temperature.

Since the 5W30 oil is thinner, it helps a car start easier and quicker during cold weather. It is also a more versatile oil for any season use, thanks to its wider temperature spread.

Conversely, 10W30 engine oil provides better protection to the engine parts against wear during cold weather.

4. Polymer

Both engine oils have the same single grade 30-weight oil base and friction modifiers to flow smoother at winter temperatures.

However, people believe 10W30 oil has more oil and less polymer, making it better than its counterpart.

Precautions To Follow while Mixing 5W30 and 10W30

Mixing two types of viscosity oils, 5W30 and 10W30 requires extra care and consideration.

If you mix two wrong types or can’t mix the right type properly, you’ll experience poor engine performance, shorter oil change intervals, or expensive repairs. Follow these tips to mix 5W30 and 10W30 seamlessly:

• Don’t try to mix synthetic and conventional engine oils as one is artificially synthesized while the other one is extracted from crude sources. Mixing them can cause a gummed-up situation which is harmful to a motor and other functioning parts.
• You can mix either two light or two heavier oils. Mixing two different weights of oil won’t let you drive efficiently and cause various mechanical issues.
• Before mixing engine oils, ensure they are suitable for the current season. If you want to mix 5W30 and 10W30 oils, choose them from the same brand.
• Oil additives help to mix two different types of oil properly. It also helps the heavier fluid to move quickly and mix with lighter oil. Oil additives offer extra protection against wear to the engine. So, you can use oil additives before mixing 5W30 and 10W30 engine oil.
• To mix and homogenize 5W30 and 10W30 properly, firstly pour 5W30 oil into the engine and then add 10W30. Avoid spilling during mixing the oil as it can make a burning scent. Start the engine and run it for a few minutes to mix the oils perfectly while ensuring optimal performance.
• After mixing 5W30 and 10W30 engine oil and driving for a while, check the engine’s oil level. If you notice insufficient weight inside of the engine, mix more oil. The oil must reach enough weight according to the car’s manufacturer’s recommendation.

Also Read: Car Shaking after Oil Change

FAQs on Can You Mix 5W30 and 10W30

Final Words

Many car owners ask if can you mix 5W30 and 10W30 engine oil as they have some leftovers. When it comes to the safety of expensive parts like engines, you should stick to the manufacturer’s suggestion.

Though you can mix 5W30 and 10W30 for emergencies, it isn’t a good practice. So forget about the leftovers and only use the particular type and weight of engine oil recommended for your car’s engine.