10W30 vs 10W40 Oil Comparison (Which Is Better?)

10W30 vs 10W40, How do these oils differ?

10W30 and 10W40 are both very similar. They’re both durable and come in different grades to work for different temperatures. Though there are similarities between them, their differences are still clear.

So we will be looking closely at these oils, what they are all about, and how different or similar they are to each other. We will also consider their functions in warm weather or high mileage engines. That way, you’ll decide better which oil suits your vehicle.

10w30 vs 10w40: What Are They?

10W30 VS 10W40

10W30 & 10W40 are oils of different grades, their components are of different grades, and they’re often referred to as “multiple weight oil.”

The number that precedes “W” is the first grade, while the one after is the second.

But not to worry, we’ll be looking closely into what these numbers mean.

1. Low-Temperature Viscosity

The initial number (before the “W”) describes the measurement of the oil’s resistance to flow. So anything below 0°C (32°F) is considered a low temperature.

These oils, 10W-30 & 10W-40, have been rated “10W”, so according to SAE grade, the “W” represents Winter. These oils work as 10W single graded oil for lower temperatures for SAE.

When an engine is cold, this number is especially important for a car’s startup to enable quick flow for lubrication. So the lower the number, the easier and quicker the oil flow.

2. High-Temperature Viscosity

The following number (after the “W”) shows the measurement of the oil’s resistance to flow at 100°C (212°F). This temperature is often considered the temperature the engine operates on.

The greater the number, the higher the viscosity level is in a higher temperature.

So at 100°C, engine oils with 10W30 contain the thickness of an SAE 30 single-grade lubricant, while oils of 10W40 contain SAE 40 viscosity.

As the temperature increases, oil of 10W40 contains higher viscosity than 10W30.

That said, engine oil with 10W-40 protects engines from wear and tear at a higher temperature.

Having considered their numbers and how they work with temperature, let’s compare the performance and application of these viscosity oils.

Also Read: 6 Best High Mileage Oil

8 Ways To Compare 10W30 Vs 10W40

The basic contrast between these two oils – 10W30 vs 10W40 is their thickness (viscosity level) at high temperatures.

So let’s separately consider the viscosity of these oils and their impact on where they’re being used and when they’re being used:

1. Low Running Temperature Or Cold Weather

As we earlier discovered, 10W-30 & 10W-40 share similar oil thickness at more reduced temperatures.

A 10W Winter rated oil will not have issues in temperatures below zero degrees to 30°C (-22°F). So you shouldn’t worry about cold weather when it comes to these oils.

However, the 10W30 engine oil that’s a little lighter works best in a colder environment.

The only challenge the engine oil faces is the engine heat because the cold atmosphere won’t give any form of thermal pressure. So instead, a lighter oil moves quickly into the engine to help cool and lubricate it.

Also, if the engine’s temperature is too low, 10W-40 engine oil may be quite thick for it because the height of the viscosity level is detrimental to your engine’s performance.

2. High Operating Temperature Or Warm Weather

Both oils, 10W30 and 10W40, run similar functions for cold-weather startups.

Still, the 10W-40 oil is thicker in hot weather, with a preferred temperature range. For each oil grade, below is the generally recommended temperature level:

  • SAE 10W-30 motor oil: -25°C (-13°F) to 30°C (86°F)
  • SAE 10W-40 motor oil: -25°C (-13°F) to 40°C (104°F)

The tolerance the 10W40 oil has for hotter temperatures indicates that it’s the best resistance for any thermal breakdown as it also reduces the formation of deposits.

So, if you navigate through a warm climate above 32°C (90°F) or your engine gets hotter than normal, then 10W40 oil is the right choice for your engine because such viscosity oil was made for hot temperatures.

10W-30 oil can be used in hot weather temperatures. But note that due to its lighter texture, it’s likely to not lubricate parts of your engine as much as 10w40 would.

3. Fuel Economy

We’ve discovered that lighter oils flow faster and easily through the engine. It also helps reduce drag and requires less energy for pushing the oil pump, which improves the fuel performance.

Also, the thinness of a 10w30 motor oil is more economical for your fuel than 10w40 oil is. And it is also very common, which makes it not too expensive.

However, if this oil doesn’t suit your car and the conditions involved in driving it, do not use it. Instead, go for the best oil that suits your engine to improve its performance and longevity.

10W30 VS 10W40

4. Oil Additives And Types

Graded oil in the likes of 10W-30 & 10W-40 has polymers that increase or decreases the rate, then it thins and thickens as the temperature changes. While some of these oils have components that reduce friction which helps economize your fuel by reducing friction, or any cleaning agent that helps clean the engine.

The ratings from these two oils are present in your everyday oil or quality ones. However, though they share similarities, their differences are clear daily, particularly between typical motor oils and artificial ones.

Synthetic Oil guarantees better protection for the engine and stabilizes the temperature. For example, 10w30 synthetic motor oil might work better than conventional 10W-40 oil to protect your engine pistons and bearing.

5. As An All-Purpose Option

10W30 motor oil is a diverse oil that works for every situation.

The temperature range it works in is more common than the 10W-40 thickness grade. Cold starts are perfectly handled as it reduces wear and tears in the engine.

This multigrade engine oil is very affordable and isn’t expensive. In addition, it simplifies the oil maintenance experience with effective cost.

6. Heavy-Duty Applications

Like commercial vehicles, this application requires an efficient oil that can withstand heat.

As for 10W-40 oil, it shoulders the responsibility perfectly because its thickness is capable of withstanding loads and protecting the parts of your engine as it heats compared to 10w30 oil with a lower viscosity.

Generally, a high mileage engine requires a thicker engine oil, especially those over Seventy-five thousand miles.

The older oil passages get, the more wear and tear they experience, and the only remedy is a high viscosity oil to help in the engine’s lubrication. So you might want to consider switching to 10w40 oil for an older engine rather than use 10w30 oil. It all boils down to how old the vehicle is.

Though this is an issue that applies to old vehicles, it isn’t true for modern engines, engines manufactured in the past ten years.

Manufacturing improvements, oil mixture, and the design of oil filters do not wear off due to fiction. Burning oil is mostly caused by seals that grow old rather than increased gaps in engine parts.

So making use of an oil with a higher viscosity may burden the oil pump, reduce the circulation of oil all over the engine parts and increase the oil pressure.

Here’s the solution high mileage oil presents.

This oil was made to handle seal-related issues in newly produced engines.

Rather than switch to 10W-40 oil after using 10W-30 oil for an old engine, you should consider a higher mileage grade of 10W-30 oil.

8. Motorcycle Use

Like commercial vehicles, irrespective of the use, 10w40 oil for your vehicle as against 10W30 oil depends on the weather temperature the vehicle will be ridden in.

The main contrast between motorcycle oil and passenger car oil is their purpose.

Vehicles have several parts the fluid protects, like transmission fluid which protects gears. In addition, the engines of motorcycles smell and use the same sump.

The motorcycle oil doesn’t only lubricate the engine; it also lubricates the gearbox and clutch. Also, commercial vehicles contain friction modifiers that cause slipping and loss of acceleration in motorbikes.

You may consider lubricants with good oil grade for your motorcycle that contains detailed formulation.

Also Read: Can You Mix 5w20 and 5w30?

Can You Use 10w40 Instead of 10w30?

10W30 vs 10W40

Yes, it is. Both oils were made to serve the same purpose. So it is safe to consider either of them for your next purchase. But there are a few differences between them: base oil and viscosity.

Viscosity means the thickness of a liquid. The greater the viscosity, the thicker the liquid, making it difficult to flow through an engine or a pipe. The viscosity of oil has to do with its thickness. Thicker fluids are commonly known to have a higher viscosity than thinner fluids.

The heat index number shows the flow at operating temperature and warm weather. The higher the rating for a certain kind of FZPNP or API-approved Oil, the car’s components will be protected from damage by excess pressure and increased temperature changes.

For 10w30 & 10W40 oil, the difference between them is their thickness at working temperatures. During cold startups, they flow well because their viscosity level is equally “10” when they react with air and other gases.

10w30 engine oil is the best fit for warming up the engine quickly because it reduces excess temperature and drag caused by cold weather. In addition, this oil helps cool off with less energy than average oil does during hot weather when it overheats.

As winter approaches, endeavor your vehicle is in perfect working condition by changing old engine oil to new ones that correspond with the season.

Also, you’ll observe the improvement in the acceleration time, so one shouldn’t hesitate to get back into the car after being out for so long or driving away from your house for some reason.

For summer, 10w40 oil is not the best option if you intend to prevent the contact of metals in moving parts because, for high temperatures, light lubricants can begin to melt. So it’s advised to keep the car cool, at least yearly.

So for your every winter driving experience, it’s best to do it with the appropriate fluids.

The 10w30 oil is the best fit for summer as it would help your engine run smoothly unless a snowy situation erupts, which is no good news for your car.

The lubricant of oil is found in the base oil; this base oil makes the oil efficient for lubricating engine parts. For instance, 10W30 synthetic contains petroleum distillates, and the 10W40 contains synthetic base lubricants like Polyalphaolefin (PAO) and synthetic mineral oils (SMO).

The two oils have common bases but contain separate physical properties that play their roles in the engine parts.

Also Read: Can I Use 10w30 Instead of 5w30?

When to Use 10w30 Oil

If you reside in a cold region, 10W30 oil is the best choice for your car because, in this region, the oil only has to deal with heat from the engine and not the one from the atmosphere. So while an engine heats up during Winter, the 10W30 oil helps reduce the engine’s temperature.

You’ll also realize that 10W30 oil is demanded more than 10W40 oil. Moreso because of its accessibility and affordability. So to those searching for an economical solution, 10W30 oil is the one for you. However, it shouldn’t be up for consideration to those residing in hot regions or experiencing summer presently.

When to Use 10w40 Oil

10W40 motor oil is the go-to choice for those who reside in hot regions or regions that are currently experiencing summer. This oil was designed to work in hot temperatures and keep engines from wear and tear. It doesn’t only deal with heat from the environment; it’s also meant for engines that get hotter than the rest.

10W30 oil can be added in hot weather. But note that it will thin out faster than 10W40 will. And as temperature increases, the inner components might not also be lubricated. So in higher temperatures, 10W40 is advised for better protection.

Mixing 10w30 With 10w40

10W30 vs 10W40

When mixing the two oils, people tend to have a mixed reaction. Though some are open about it, saying it isn’t a bad idea entirely, provided you don’t reside in a cold environment, because even though you put a conventional and synthetic type of these oils together, they cause no damage to the car.

Nonetheless, there will be no issues if a quarter of your usual oil is poured into the mix.

Several car owners and mechanics avoid mixing 10W-40 with 10W-30 for many reasons. And one of the reasons is to avoid a decrease in the pressure of the oil when arriving at high rev, causing the spinning of a bearing or two.

Take note also that the mixing of oils could affect your car’s fuel consumption and warranty. Though 10W40 and 10W30 have similar functions during cold startup, one is a little thicker and would be less efficient in most high temperatures conditions.

Unless you’re left with an option of combining them, otherwise do not mix the two oil. Finally, and most importantly, have spare engine oil when going on a trip, so you wouldn’t have to mix anything.

Also Read: Can I Use 5w30 Instead of 5w20? (+ Key Differences)

Frequently Asked Questions – 10W30 vs 10W40

What happens if I put 10W40 instead of 10W30?

For the two oils, 10W30 works better in cold climates, while 10W40 helps prevent wear and tear in hotter temperatures.

What is 10W40 oil used for?

Thicker oils like 10W40 are good for oil leaks or old engine burning. So we recommend Mobil™ 10W-40 oil for the car’s over 75,000 miles or synthetic blend engine oil for cost consideration.

Can I use SAE 30 instead of 10W40?

In all, 10w40 oil may not be recommended for your car; I’ll recommend SAE 30 for the lawn mower. What is that? Lawn mower engines accept oils with a thickness rate of 30. The reason is that 10W40 has a higher thickness level, and the engine may not easily lubricate itself.

Is 10W40 good for high mileage?

For vehicles over 75,000 miles, Pennzoil High Mileage SAE 10W40 oil is designed for them, especially cars experiencing oil burn-off and leaks, and old engines are more prone to wear and tear than new ones.

Which is more fuel efficient, 10W30 or 10W40 engine oil?

Actually, thin oil gives better gas mileage as it reduces viscosity, making it easier to pass through parts.

Can I mix 10W30 and 10W40 oil?

Yes, you can. They tend to cause no harm to your vehicle when they come together. Peradventure, you had to mix synthetic oil with conventional ones; it still wouldn’t be a terrible idea. Though if tested at the laboratory, it wouldn’t come out as 10W30; still, it wouldn’t result in any harm.

Is 10w 40 heavier than 10W30?

10W40 is thicker than 10W30 at high temperatures. Though they have similar features, the only difference is their viscosity level.

What is 10w 30 recommended for?

First, let’s consider what 10w-30 oil is. It is a multigrade engine oil fit for heavy-load engine parts because of how well it works in warm temperatures, maintaining the engine’s performance. Also, this oil’s viscosity is grade 10 for low and 30 for higher temperatures.

Is 10W30 good for summer?

Your vehicle is safer when it uses an oil a little thicker in a hot atmosphere, oils like 10w-30 rather than 5W30. In summer, engines require thicker oil because of the heat. So to avoid the oil from thinning out, thicker oil is recommended.

Conclusion – 10W30 vs 10W40

10W30 and 10W40 are quite similar. The only possible difference is the engine load and temperature fluctuation.

For average weather, the two oils are a good fit. Your choices only tend to rise a little when you approach high-heat situations.

Whatever the case, ensure to always fall back to your instruction manual for its recommendation on engine oil. Never take your eyes off the oil level, so you have enough to lubricate the engine. And should you feel your engine needs a new oil type, endeavor to consult your mechanic.

Scott Greene is a seasoned automotive technician for over 5 years and has been deep into advanced automotive diagnostics for a couple of years. He Loves writing about Automotive Diagnostics and Repair, Trouble codes, Buyer guides for various car parts and accessories, and lots more. 

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