5W30 vs 5w20, 5w40, 10w40: Which Grade Motor Oil Should I Use?

What oil should I use in my car? Most car owners take their vehicles to the garage for the oil change. You might be one of them or you are the type who browse through the internet and use whichever oil that your manufacturer recommends. Although either scenario seems to be okay, it is important to know a little more about what you are feeding into your car and having information concerning the best oil for your car. 5w30 vs 5w20, 5w40, 10w40: which grade motor oil should I use? If that is your question, then you are on the right path. It is necessary to compare the properties and specifications of engine oils so that you can know which oil to use in your car.

What Does xWy Actually Mean?

X and y stand for the viscosity of the oil while the W stands for winter. The Society of Automotive Engineers (SAE) established the numerical code system which they use to grade the motor oils in accordance with the characteristic of their viscosity.

Due to the fact that the viscosity of oil changes with the change in temperature, several oil grades were established in order to provide protection for the engine of the vehicle across various temperatures. And that is why, on the label of the oils, you will see something like SAE 5W30, SAE 5W20, SAE 5W40, SAE, 10W40.

The number before the W describes the viscosity of the oil when temperatures are at their lowest. If the number is lower, then it means the oil is thinner and thus, best for a cold start or cold temperatures performance. The number that appears after the W describes how thick the oil is when the engine is operating at normal temperatures.

Multigrade oils such as 10W40, 5W30, are normally used widely because of the fact that, under all but extremely cold or hot conditions, they are thin to allow them to flow at temperatures which are low and at the same time, thick enough to allow them to perform very well when the temperatures are high. This means that the choice of viscosity would be different depending on the temperatures of where you stay. Different vehicles require different xWy and thus, you will have to consult with your manufacturer’s manual.

The x and y according to SAE, can be represented by viscosity characteristics ranging from 0, 5, 10, 15, 20,25, 30, 40, 50 and 60. Viscosity is the resistance of liquids to flow. Those which are runny and very thin are normally given a viscosity that is lower while those which are consistent and very thick like honey, are given a high value of viscosity.

It is important to remember that, engine oils change their viscosity when put in different temperatures, depending on the weather outside. As concerning the kinematic viscosity, the numerics are normally assigned based on the ability of the oil to flow via an average orifice when the temperature is regular. If it takes the oils longer periods to pass through then it means that the SAE code assigned will be high because the viscosity is high meaning, 5w30 has a higher viscosity than 5w20.

Viscosity Grades

The viscosity grade of oil is determined by SAE, the Society of Automotive Engineers. It separates oils into mono or single grade and multigrade. For an oil to be termed as Multigrade, it has to fulfill two viscosity specifications and the viscosity grade will consist of two numbers such as 5w20 with 5 representing the low-temperature viscosity or winter, and 40 referring to the high-temperature viscosity or summer. Most of the engine oils that are available in the market are Multigrade. Monograde oils are normally restricted for a specific usage like lawnmower oils.

In comparison, Multigrade oils seem to be the preferred option for modern engines. They are able to keep the engine operating at an optimum viscosity range and at the same time, offer lubrication protection and consistent response. When it comes to single grade, they can be the best option in case the equipment in question is able to provide excellent constant control of temperature and oil cooling.

1. Single Grade

As defined by the SAE J300 type of classification, the single grade oil only covers a single requirement and thus, cannot be used as polymeric viscosity index improver. According to SAE J300, there are 11 viscosity grades with 6 being considered as winter grades and thus given the W designation.

The single winter grades, its dynamic viscosity are normally measured at various temperatures which are cold. Based on the coldest temperature that the oil is able to pass through, it is then graded as SAE viscosity 0W, 5W, 10W, 15W, 20W or 25W. The lower the temperature the oil can pass through, the lower the viscosity grade.

For nonwinter single grades, its kinematic viscosity is normally measured at a 100 degrees Celsius temperature. Based on what viscosity range it falls in at that particular temperature, the oil will then be able to be graded as SAE 20, 30, 40, 50, or 60. For SAE grade 20, 30 and 40, its minimum viscosity is measured at 150 degrees Celsius. The higher the SAE grade is, the higher the viscosity of the oil.

2. Multi-grade

For multigrade oils, as opposed to the single grades which cover single requirement as stipulated by SAE J300 system of classification, they are able to cover multiple SAE grades and thus, can be used over a wide range of temperatures.

They are made from a blend of low viscosity oil which are added additives known as Viscosity Index Improver (VII). The VII improves the viscosity and temperature characteristics of oils. When oils have these additives, they get good starting and friction properties of thin oil at temperatures which are low with lubricating properties which are good of oil that is more viscous at higher temperatures.

How the VII works in the multigrade is that, when the temperature is low, they are able to curl themselves into a ball that is very tight which enables it to move freely with the molecules of the oil. With an increase in the temperature, they expand and form a large stringy structure that restricts the oil’s normal flow. When there is a reduction in the temperature, they settle back into their original shape.

Advantages Of Multigrade Oils
  • It is faster full pressure lubricant over a variety of temperatures
  • You can use one oil for a whole year
  • It has improved low-temperature starting
  • It has less battery drain when starting the vehicle on cold starts
  • It has excellent high-temperature performance
  • It gives the engine improved overall fuel economy with faster warm-up and less idling time
Disadvantages Of Multigrade Oils
  • Polymer shearing might occur under shock load conditions or high stress
  • Low-temperature leaks of oil may occur when the engine is badly worn out.

More Details: https://en.wikipedia.org/wiki/Motor_oil

Choosing the Right Type of Motor Oil

There are various types of motor oil in the market and picking the right one for your car might be daunting. Remember that, each oil is meant for a certain purpose and thus, to pick the right one for your car, you will have to understand the significance of the viscosity ratings, oil additives, and classification codes.

1. Oil Additives

​This is going to help in ensuring that the engine of your car keeps cool, corrosion free, and clean. There are various refiners which blend in various additives and they can be able to account up to 25 percent of the total amount that the oil costs.

2. Viscosity Ratings

​Oil is identified and rated by its viscosity which then determines how it is going to flow. Multi viscosity is what modern vehicles run on. The lower the viscosity the thinner the oil is and the easier it is able to flow. To find out the viscosity of your particular car, check in the manufacturer’s manual.

3. Classification Codes Of Oils

​The starburst that you will find on the container of the oil denotes that, the oil meets the current standards in regard to engine protection and fuel requirement standards

Questions To Ask Yourself Before Picking The Oil

  • What are the oils which your vehicle has been running on? If it is fine and giving you no problems, then there is no need to change it.
  • What is the recommended oil in your manufacturer’s manual? If your vehicle is still within the warrant, if you decide to use an alternative oil other than what is specified by the manufacturer, you are going to void the warrant.
  • What is the temperature of the area you reside in? Is it plain or mountainous? Do you encounter temperature change? If you use multigrade oils, they will be able to cater to a variety of temperatures. The lower the number before W, the better the oil is going to work in cold
  • weather.
  • What is the age of your car? If your vehicle has been running on single grade oil for most of its life, then it means that it has built up a lot of sludge as some of such oils don’t have detergent. And in case you suddenly switch to multi-grade, it will free all the sludge which might affect the engine in a negative way.
  • What is the shape of the engine of your car? If your car is very old and it has always been running on single grade oil of 30 or 40, then multigrade will not be able to lubricate it well as the parts have become smaller, with wider spaces in between them. In order to keep the oil thick enough to be able to fill the gaps, you will have to switch to a heavier single grade oil as the vehicle gets older.

1. Conventional Oil

It is the oil which is used especially in dealerships and it tends to be the cheapest of the auto oils in the market. Most of them adhere to SAE and API standards, but at the same time, offer little in terms of additives. If you are religious about frequent oil change and own a low mile, but well broken in engine, then this is the oil for you.

2. Premium Conventional Oil

It is the standard new oil with most leading brands having one for SL or the highest level of service. You will find them available in most viscosities in the market. Some manufacturers will specify in the manual 5w30 or 5w20 but there are those which require up to 10w30. The three specified ratings tend to cover every light-duty vehicle on the road but it seems to be changing as engines are becoming more fussy and precise about certain types of oil.

3. Full-synthetic Oil

This is oils which are manufactured specifically for engines that are high tech. If they are able to pass the stringent tests which are indicated on their labels, then it means that they will offer long-lasting, superior performance in all the critical areas, from protection on engine deposits to viscosity index. At low temperatures, they are able to flow better and at the same time, at high temperatures, able to maintain peak lubrication. While high quality full synthetic oils cost three times the cost of other oils, they are not a necessity for most engines. It is best that you stick to the manufacturer’s manual. It is not a must you use full synthetic oil as it might just be an additional cost which might not add anything to your car engine.

4. Synthetic Blend Oil

The synthetic blend oil is a premium conventional oil which has some synthetic in it. Most of them are blended to offer the engine better protection during heavy engine loads that cause high temperatures in the engine. They are most popular with SUV and pick-up engine drivers due to the fact that they offer better protection and yet, cost just a fraction as compared to some conventional oils.

5. High-Mileage Oil

More than half of the vehicles on the road have done more than 75,000 miles on the odometer. And that is what made most oil manufacturers come up with the high mileage oils which have seal conditioners added to it to ensure that it increases and expands the flexibility of internal engine seals. The oil can either be conventional or synthetic. The conditioners which are added are very precise and this is capable of benefiting some engines while others don’t

Comparison Between 5w30 vs 5w20, 5w40 and 10w40

#1. 5w20 vs 5w30

What Is The Difference?

The main difference between 5w20 and 5w30 is that the former is less viscous or thicker. When you happen to pour it in the engine, the 5w20 will be able to create less friction due to its thinner viscosity, meaning, the resultant drag is less in the engine parts such as valve train, pistons, and crankshaft. With this said, there is a partial bump which is created in the fuel economy.

The oil pump is able to move it from the oil pan to the rest of the engine easily due to the runnier nature of 5w20. That is what makes the 5w20 a better option for people who stay in climates which are cold.

The 5w30 is the best choice if you stay in climates which are hot where oil which is thinner tends to break easily under high temperatures. The more the motor oil is viscous, the better it is going to be in a position to resist the heat and not be able to break down. This means that the 5w30 is going to provide better protection for the engine on the overall as compared to 5w20. The 5w30 is widely used due to the fact that it works great with the various selection of vehicles with different types of engine, with the oil covering a broad range of various temperatures.

Which Oil Should The Vehicle Owner Use

When choosing the best oil for your vehicle, you will have to take into consideration certain factors. Even though when it comes to the levels of protection there is no much difference between the 5w20 and the 5w30, there is a slight difference when it comes to viscosity. If you stay in an area which is hot, you are better off using 5w30 motor oil due to the fact that, it operates better in high temperatures and thus the engine will be provided with better protection.

But if you stay in cold areas, then you will need a thinner oil, which will be able to heat up easily, meaning, the 5w20 will be an option which is better. And in case you live in a region that doesn’t experience extreme temperatures, then you can use either of the two.

#2. 5w30 vs 5w40

What Is The Difference?

5w30 is one of the most commonly used types of motor oil due to various reasons. It is one of the oil which works well with a variety of vehicles with different engine types. The oil is also able to cover a diverse range of temperatures, but mostly, it is good for warm temperatures. Most of the time it works well, irrespective of the vehicle and the temperature.

Although the 5w40 is not a common motor oil like the 5w30, it is one of the oils which has some features that are great at optimizing the engine like protecting the engine from sludge buildup, deposit, and damage. It also ensures that the engine comes back to life when in colder environments and the oil is able to circulate well in temperatures which are freezing.

When the engine is in motion, the oil gets into the moving parts easily. In cold weather, the5w40 normally acts as a single grade oil, but the good thing is that it doesn’t become thin more than 40 rated oils when the temperatures are hot.

Which Oil Should I Use?

When you have to choose between the 5w30 and the 5w40, it seems that most people tend to prefer the 5w30 because it has a smooth effect on the oil pump and also, it has a suitable flow through the engine when it is hot.

Both the oils work great for being able to provide the much-needed lubrication to the parts of the engine whenever you start the engine. The number 5 in both the oils represent the viscosity which is the same when the engine is cold, that is, the start-up temperature. The 30 in the first oil represents a viscosity that is lower when the engine is in operation at high temperatures as compared to the 40 in the second oil which has a higher viscosity.

If you are wondering which oil between 5w30 and 5w40 to choose from, then you are better off choosing the 5w30. But in case it is unavailable or too expensive to afford, you can always opt for the 5w40 which is equally good and there will be no engine damage

#3. 5w20 vs 10w40

What Is The Difference?

The 10w40 is a fully synthetic high viscosity motor oil which is designed for motorcycles to protect the sports bikes clutch, engine, and transmission. It has good viscosity, protecting the engine well in light and severe riding conditions. It gives the transmission and clutches additional protection. It has solid heat and cold thinning temperatures. When used, it cleans the engine as it lubricates the necessary parts. With constant use, it is going to lengthen the life of the engine and maximize its performance. The downside of the 10w40 is that it is only meant for motorcycles.

The 5w20 is a good motor oil which works well with most motor vehicles which require 5w20 motor oils such as imported models, car models and GM cars. So if you have a car that you use to go to school, get to work or go buying groceries, then this is the right oil for you. But in case your car is a commercial one, towing, or race car, then it might not be the right one for you.

When Should I Use?

It will be best to use the 10w40 in summer as it will likely help the oil to be able to stick to internal components in high temperatures thereby avoiding the wear and tear from metal to metal contact when the parts are moving. In cold weather, it will be best if you went for the 5w20. Check out the manufacturer’s manual and find out which oil specification is given.

#4. 5w40 vs 10w40

What Is The Difference?

The difference between the two is that one is thicker than the other. The 10w40 tends to be thicker than the 10w40 when cold. But at a higher temperature, they are both operating at the same viscosity. If the vehicle requires a 10w40, then there is no need to use a 5w40

The 5w40 is a very thin oil which will get a vehicle’s parts moving easier and be easily lubricated when starting it up. The 40 is an indication of the oil being a little bit thicker than the average motor oil, which is normally at 30 and thus, it lubricates the engine more than what the average oil does.

For 10w40 motor oils, they tend to be a bit thicker than the 5w40 but still, rather thin and tend to work well in lubricating moving parts of engines during startup. The 40 denotes that the oil will be a little thicker as compared to an average oil when exposed to the heat of an engine which is running.

When Should I Use?

You will use the 5w40 oil when trying to support high mileage engines due to the fact that, it is thicker when heated than the ordinary oil and thus, will be able to lubricate the parts which are moving inside the vehicle which is worn down as a result of age or strain. In most cases, you will utilize it on vehicles that are high mileage in climates which experience winter of 5 degrees Celsius. It is good for cold engine starting up, but it might be less reliable in climates that experience temperatures which are freezing.

Utilize the 10w40 motor oil in vehicles which have higher mileage due to the fact that, this oil is thicker when the engine is hot and thus, it helps in lubricating older moving parts. It is an oil that you should utilize to start up vehicles in winter climates of temperatures about 10 degrees Celsius. This 10w40 is not a reliable oil for engine startup in colder climates of winter as compared to the 5w40 oil.


When you ensure that your car has the right engine oil, you ensure that it has the correct cooling, lubrication, cleaning, and internal component protection. Get the right specifications and amount of engine that is right for servicing your type of car. Check out the 5w30 vs 5w20, 5w40, 10w40 and choose the right one for your vehicle depending on the range that your car manufacturer has specified in the manual.

Each vehicle engine is manufactured around a certain engine oil grade viscosity and a specific specification. The various stresses and strains in a motor vehicle are behind the variety of specifications in the market. In order to maintain your engine well in terms of life span, efficiency, and performance, you will need to stick to the oil which your engine was designed around.

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