Even though most of us take the vehicle to the mechanic for oil change and maintenance. It is never wrong to educate yourself. Both the oils – 5W20 and 5W30 motor oil – work well in hot and cold temperatures.

The main difference between the two is the viscosity. Viscosity is the resistance of the motor oil to flow. The higher the number of the number on the product the slower it is to flow. The Society of Automotive Engineers has a code to differentiate motor oils based on their viscosity. They begin from a low of 0, 5, 10, 15 20, 25, 30, 40, 50 and 60.

The oils with low viscosity are assigned a lower number like 0, 5, 10, etc. The oils with a honey-like consistency get a higher number. This rating is measured at 0°C. Thus, in this case 5W is the viscosity of the oil at 0°C. But it is too thin for automobiles at a regular temperature. Thus, oils have different versions. It should also be kept in mind that the viscosity measurements of the motor oil change with varying temperatures or weather.

These kinematic viscosities are assigned to the oils under regular temperatures travelling through regular orifices. The longer it takes for the oil to flow through the higher the SAE number code. Applying this information to the 5W20 and 5W30 motor oils. The 5W30 has a higher viscosity to 5W20 oil.5W20 vs 5W30 in 2020

Now let us understand what does “W” stand for. The alphabet W stands for winter and it represents the cold viscosity of the motor oil. The number before the W rates the performance of the motor oil in cold climate.

If you live in cold place like Russia, Korea, Canada or the poles your automobiles engine may be subjected to frigid conditions while parked or driving. If you have used a motor oil that has a high cold viscosity (in this case 5W), it will be too thick to lubricate the engine. This will affect the fuel efficiency and the engine will be compromised.

The number after the “W” represents the hot viscosity of the motor oil. Hot viscosity is the motor oils resistance to heat. There are many variants in the oil type as engines tend to get hotter than cold.

Purpose of Motor Oils

To decide which of these two motor oils is better – let us understand what do motor oils do? Like grease, motor oils lubricate the surfaces of the engine minimizing friction. The oil not only prevents the parts from grinding against each other causing friction and overheating.

The oil also washes and cleans the engine. It gets rid of the silicon oxide and acids that occur naturally during the engine’s lifespan. The process of oxidation is inevitable considering the atmosphere of the earth and the dust that makes its way into the engine while driving.

These waste materials get collected in the engine and are washed by the motor oil. You see the waste leave the engine when you change the oil in the form of a sludge. If you do not change the oil, the motor oil breaks down and forms a pasty, sludge-like substance.

This affects the efficiency of the engine. This process is natural and inevitable. Yet it can be controlled by regular check-ups. clean-ups and tune-ups. Motor oil is like the lymph and blood in out body. These fluids cool the body, bring nutrients and oxygen to the cells and take away toxins. Motor oils thermoregulate, condition and lubricate the engine and take away the dirt, dust and other residue.

5W20 vs 5W30 Motor Oil

We will compare these two motor oils based on;


The difference between the two motor oils is their viscosity. Motor oil is put into an engine to lessen the friction 5W20 vs 5W30 in 2020and produce less drag on all engine parts. It forms a thin film over the pistons, crankshaft and valve train. This lubrication helps the engine run smoothly increasing the fuel economy.

5W20 is lighter thus creates less friction and drag. Its runnier nature also enables the oil pump to deliver it from the oil pan to rest of the engine. The motor oil is ideal for cold places. The viscosity grade of this oil is 8.9 at 100°C.

5W30 is thicker and better suited for warmer climes. The viscosity grade of this oil is 11 at 100°C. Thinner oils break down at higher temperatures. This oil is more viscous and resists break down due to heat.

At the temperature of 40°C – which is the normal temperature of a vehicle – the viscosity of 5W20 motor oil is 49.8 and viscosity index is 160. While that of 5W30 oil is 61.7 and its viscosity index is 172. Both oils have a flash point of 230.

Viscosity index is the motor oils resistance to become thinner at higher temperatures. Flash point is the temperature of the vapors over the oil to ignite when exposed to a source of ignition. For motor oils it is usually 225°C or 440°F. These oils meet and comply the ASTM D92 and D93 standards.

5W30 motor oil offers better protection than the 5W20 as it is compatible with a diverse selection of automobiles and engine types. It can also withstand a wider range of temperature variation.

Multigrade Motor Oils and Different Climes

Both these oils – 5W20 and 5W30 – are multigrade. These oils feature two numbers or grades in viscosity ratings. These viscosity ratings are observed at different temperature conditions.

These oils carry a mix of polymers in the oil. These polymers expand in size as the temperature rises or contract when it falls. This in turn, raises or reduces the viscosity of the oil.

Viscosity rating is notated with “XW-XX”. Here, the XX refers to viscosity when cold and is measured at 0°F or -17.8°C. The lower this value the more fluid the oil will remain at low temperatures. Thus, it will be easier to pour and pump. The “W” stands for winter.

For example, motor oils such as 0W20 and 5W30 make it easier to start up the engine in colder regions. They also 5W20 vs 5W30 in 2020protect the engine while driving in these conditions. These synthetic or hi-tech fluids are suitable for recent models of automobiles.

Consider this notation – “XX W – YY”. The YY refers to viscosity when hot which is measured at 212°F or 100°C. These oils are resistant to thinning as the mercury rises. They lubricate the engine well and offer a better mileage too.

For example, motor oils such as 15W40 and 20W50 are meant for use in hot countries. As their viscosity makes them suitable for the climate and older engines. To decide which motor oil is suitable for your vehicle check what kind of climate you are going to be driving in.

Effect on Gas Mileage

The lesser the viscosity of the engine oil the thinner it gets; affecting the fuel efficiency of the automobile. The thinner the oil, lesser the lubrication of parts, and higher their wear. This also affects their performance due to friction.

The quicker the wear, the more frequently you have to replace these parts raise the cost of maintenance. The lack of lubrication also affects the conversion rate of the gasoline leading to higher consumption.

5W20 motor oil has low viscosity thus becomes thinner at the normal running temperature of an automobile. Even though this engine oil will reach hard to reach spots due to its texture and properties. Eventually it will get too thin to reduce friction effectively due to spikes in temperature. This will have a huge impact on your Miles per Gallon (MPG) fuel economy.

On the other hand, 5W30 motor oil functions better in higher temperatures. It does exactly same functions at these temperatures without breaking down. This leads to a better fuel efficiency and engine performance.

As per Expert Recommendations

As 5W30 motor oil is thicker it will offer more resistance than 5S20 in cooler temperatures. This will lower the horsepower output and fuel economy. If the engine components are specifically designed for 5W20 motor oil then you risk engine damage using 5W30.

As per notations

5W20 and 5W30 motor oils are preceded by a common notation 5W for cold viscosity. This means that they both are meant to be used in cold conditions. This also means that they will behave the same way in cold conditions, i.e., offer sufficient lubrication and protection to the engine. The values of hot viscosity will adjust according to the ambient temperature to provide optimal conditions to run the engine.


In conclusion, Synthetic motor oils are flexible and work equally well to bring you better mileage and protect the 5W20 vs 5W30 in 2020engine. But if you are wondering which one is best for your car. It would be prudent to consider the climate and weather your automobile will be subjected to before getting the motor oil.

Understand the strengths and weaknesses of your engine and its requirements. Match them to the characteristics, strengths and weakness of the motor oil. Study and understand how the motor oil will respond to the conditions you are going to drive through and then pour the oil in the engine.

It would be smart to study and consider the parameters such as the viscosity, viscosity index, and the suitable temperatures for both the oils before buying one for your car. If you are going to drive through regions with a low average temperature and frigid conditions then 5W20 is ideal for you.

If you are going to drive through varying degrees of temperature but the drive will take you through warmer or hotter climes then 5W30 motor oil is better suited for your automobile. Just to be on the safe side consult your automobiles manufacturers guide and auto mechanic.