10w30 vs 10w40 Oil: What You Should Choose

When you have to choose a certain type of oil for your engine, you may hesitate. What should you choose ? 10w30 vs 10w40 oils can be recommended by your vehicle’s manufacturer. That’s normal. They are some of the most popular oils on the market. The confusion begins when we are not sure about which one to choose. 

Both oils will work well in cold and typical weather conditions. They are also adaptable to multi-grade oil. Although they may appear similar, one is actually preferred for particular situations and ambient temperatures. But what distinguishes 10w30 from 10w40 motor oils, and which is preferable? 

In this article, we will take you through the sections individually to help you understand the 10w30 vs. 10w40 debate. At last, you will have enough information to choose the oil for your truck.

Why is the weight of oil important?

What is oil weight?

Oil weight is the term used to describe the viscosity of the oil. It relates to the ability of the oil to flow at low temperatures while maintaining its protective properties at high temperatures.

To create the lubricating layer between the engine’s metal components, oil viscosity is required. It must be thick enough to create a film that keeps engine parts apart while remaining at a low enough level to prevent excessive energy waste. 

Oil’s viscosity fluctuates as temperature changes. Viscosity decreases with increasing temperatures (thins) and increases (thicken) with decreasing temperatures. In cold weather, thin oils have a lower viscosity and pour more readily than thick ones, which have a higher viscosity and pour more slowly.

Why is it important?

Due to internal friction in oil, viscosity influences heat generation in bearings, cylinders, and gear sets. 

It governs the sealing effect of oils, the oil consumption rate, and the ease with which machines can start or operate at different temperatures, particularly in cold climates.

Should I buy oil with a high viscosity index?

The most popular oils are 10w30 and 10w40, and they have a high viscosity index. But is it good for your engine ? Given the information we gave before, you would believe that a thicker oil will provide better defense. Well, not really, actually.

The right viscosity grade in an oil is essential for maintaining the separation of metal parts in an engine. Having stated that, a thick oil is undesirable since it generates excessive internal frictional drag. This produces more heat, which thickens the oil (oxidation), reduces horsepower, and can also degrade engine performance.

What are exactly 10w30 vs 10w40 oils?

10w30 and 10w40 oils are what we call high-viscosity grade oils. They both contain polymers. Both can be found in their purest conventional form or premium synthetic grades. 

For summer use, either 10W30 or 10W40 is OK, while 10W-40 motor oil will better safeguard your engine. You will have a better understanding when you will know the term completely. 

Understanding “10”, “W,” and “30/40”

The viscosity rating for 10W30 in cold temperatures is 10. The ability of an oil to continue to resist thickening and solidify at absolute zero is shown by this number.

The oil is thinner as the number lowers. A product with a 0 or 5 cold weather rating will be thinner and flow more easily than one with a 10 or 20 rating.

Winter is indicated by the letter “W” after the number 10, which serves just to inform you that the first number represents the viscosity rating for cold temperatures. 

They used to produce motor oils for both cold and warm temperatures decades ago. These were referred to as winter and summer grades. These oils were of straight-grade. Low viscosity oil in the SAE 10W grade was very prevalent throughout the winter, whereas SAE 30W grade was more frequently used in the summer (higher oil viscosity).

At the end, the number 30 and 40 indicates the thickness and thinness of the oil, or you can also call it ‘grade designation.’ 

Pros & Cons of 10w30 vs 10w40

Your decision to buy a certain type of oil is based on the manufacturers’ recommendation first. But if you want to choose by yourself, then you should choose depending on the purpose. Knowing the pros and cons of both oils can help you choose your oil wisely before you get your truck on the road. 

Pros & Cons of 10w30


  • Low viscosity in cold temperatures 
  • It will be a better option for vehicles operating in hot climates.
  • It is preferable for stop-and-go driving.
  • It is a better option for vehicles that frequently transport large loads.
  • A little less expensive.
  • Works well in vehicles with high mileage.
  • Ideal middle-of-the-road oil for everyday use in all temperatures.


  • It will not be as good as other oils in hot weather, with high temperature.
  • Older vehicles do not receive as much protection.
  • Not as suitable for small engines.

Pros & Cons of 10w40 


  • Even in scorching climates, oil stays thick enough to protect the engine.
  • The thickness is an additional barrier between surfaces, providing slightly more protection for worn parts.
  • It aids in increasing fuel efficiency.


  • It could not last as long as thinner oils. As a result, it might not run as long in your engine.

Remember though: it is always better to consult your professional mechanic if you don’t understand your vehicle’s characteristics. 

10w30 vs 10w40 – Key Factors for Your Choice

When it comes to choosing between 10w30 vs 10w40 motor oils, there are minimal differences in terms of specifications. They differ more in terms of temperature variations and engine load, than in structure.

Either engine oil grade should function properly in moderate weather. When you start encountering high-pressure circumstances, your options will become more crucial. 

Just remember to consult the manual if you have any doubts. 

10w30 vs 10w40- Difference in Viscosity

When talking about viscosity, we all know that oil is thicker than water and has more viscosity. The proper oil viscosity is necessary for the motor in your car to function properly. The oil must be able to withstand a range of temperatures and be flexible enough to adapt to any circumstance. 

The oil may soon become too thin and unable to protect the interior components adequately; if your engine creates excessive heat.

For 10W-30 and 10W-40, the oil’s viscosity is the same at lower temperatures. However, the polymer additive mix makes 10 w 30 oil thin more gradually than 10 w 40 oil as the temperature rises. #40 motor oil is twice as thick as #30 when measured at 212°.

What if you drive somewhere like Phoenix, Arizona? You want an oil that provides higher high-temperature protection in a warm climate. An SAE 10W-40 would be more appropriate in that situation. 

Also, if you have to choose between these two types of oils, you should probably use an SAE 10W-30 if you reside in a chilly climate. 

10w30 vs. 10w40 – Difference in Price

The average price per quart for 10w-40 motor oil is about $5. The average price per quart for 10w-30 motor oil is about $3.50.

However, based on the package size, the two oil types have different current market pricing. For instance, the price of a 4L synthetic 10w40 motor oil ranges between US $10.20 and $12.00 per piece, whereas the price of GL 10w40 engine motor oil ranges from US $1.00 and $4.00 per piece. A 5-quart pack of 10w30 synthetic Castrol GTX high mileage is priced between $19 and $25.

10w30 Prices

10w40 Prices

10w30 vs. 10w40 – Difference in Fuel Economy

A thin oil is more fuel-efficient since it runs through the engine more quickly, minimizes drag, and uses less energy from your oil pump.

Accordingly, 10W-30 motor oil, lighter than 10W-40, gives greater fuel efficiency. This is a valuable statement whether you’re buying a quart of oil or a 55 gallon drum of 10w30 motor oil.

Many truck drivers prefer it over 10W-40 since it requires less energy for the engine to pump. If the manufacturer has not recommended it, it is not a good idea to use this type of oil to improve gas mileage. When choosing the less expensive alternative, consider the potential trade-off between engine longevity and fuel efficiency.

10w30 vs 10w40 – Difference in Applications

Engine oil that can withstand excessive heat is needed for heavy-duty applications (such as commercial trucks).

The 10W-40 motor oil is a good fit in this situation. Compared to 10W-30 oil, which has a lower viscosity, this thicker oil is better able to handle greater loads and continue preserving engine parts as temperatures rise.

What should you choose?

10w30 vs 10w40, what should I choose ? It depends on your car and driving style. For older engines and high temperatures, 10w-40 oil is best. For modern engines and increased fuel efficiency, 10w30 oil is a great choice.

Since 10W-40 oil is an all-purpose oil that can endure a wider variety of temperatures, we recommend you use 10w40 oil. It protects your engine from leaks and wears and tear. 

Mobil 1 High Mileage Full Synthetic Motor Oil 10W-40, 5 Quart, Gray

as of December 4, 2022 9:05 pm

The mission is to supply your car with the oil it needs to operate at peak efficiency throughout time. Consult a skilled mechanic who is familiar with the make and model of your car if you are unsure which oil is ideal for it.

Can I mix 10w30 and 10w40?

If you ask any random people with no expertise on any vehicle or trucks, they might suggest you mix it. However, experts advise it otherwise because of different reasons. 

First, mixing motor oil grades can cause a drop in oil pressure when the engine runs hotter. Because of the spinning, this problem may cause a bearing to fail.

If you mix engine oils, your car’s warranty may be voided. Even though both work equally well in cold weather, one is thicker in warmer climates. Unless there is an emergency, you should not mix the oil grades and subject your engine to additional wear. This situation can be avoided by bringing engine oil with you.

Can I use 10w40 instead of 10w30?

Yes. The oil will stay in place and won’t leak out or spread throughout your engine if you use 10W40 instead of 10W30. Both 10w30 and 10w40 oil selections are suitable for your automobile, but 10w40 oil is recommended if your vehicle has high mileage. 

10w30 is more viscous than 10w40. With thicker oil, older engines can endure higher temperatures and wear and tear more effectively.

However, this has the drawback that changing the type of oil is much more difficult when driving.

Final words on 10w30 vs 10w40

Your engine’s efficiency is significantly affected by motor oils. They decide how well you can withstand frigid temperatures and whether or not they emit pollutants that are bad for the air. While 10w40 motor oil performs better in colder climates, such as during winter travel at high elevations or in other harsh climates, 10w30 motor oil is better for typical, warm-weather driving situations. 

So, when we talk about 10w30 vs 10w40, many will go for 10w40. But it really depends on your vehicle and the temperatures of the region you will be driving in. Also remember that you should always consult your manufacturer or a professional for a better recommendation.