5w30 vs 5w40 which engine oil is best to use for your car?

5w30 and 5w40 are some of the most popular types of oil used for car engines. These oils have universal characteristics that allow their use in various engines.

Below we will explain, in detail, what each type of oil means, the characteristics of each type as well as the differences between the two types of oil.

The combination of both coefficients (5 and 30 or 40) in the labeling means that the oils can be used throughout the whole year regardless of the season. For this reason, 5w30 and 5w40 oils are very popular among cars.

Synthetic, semi-synthetic, and mineral car engine oils.

You will often see on the label of the oil or the packaging the words: Full synthetic, semi-synthetic, and mineral

Synthetic oils are by far the best choice to use, especially in modern car engines because they are different from mineral and semi-synthetic oils in specific processing methods.

Synthetic oils have excellent resistance to extremely low and high temperatures and provide better protection from engine wear and are, of course, more expensive than the rest.

The engine is directly affected by the performance of the oil lubrication. That is why many drivers are always wondering what oil viscosity they should use in their engines for protection, especially in cold winter temperatures. Here, you can find more info about engine oils

What does 5w30 engine oil mean?

One of the common oil types is SAE 5W30. SAE is an abbreviation of “Society of Automotive Engineers“. The mark 5w means viscosity index at low temperatures. The smaller the number, the thinner the oil and the better the starting performance of the engine at low temperatures. 30 means fluidity in summer at high temperatures, the high-temperature characteristics of the oil, and its ability to protect moving parts during internal combustion engine operation

The purpose of engine oil is to protect the car’s engine in winter when temperatures are low so that the oil operates without difficulty during cold start and is sufficiently dense to keep the engine at the same temperature operation.

The aim is to reduce the viscosity of the oil at low temperatures and increase it at high temperatures. This allows the same oil to be used throughout the year.

Also, the aim is to have the same beneficial properties in higher temperatures.

There are engine oils that meet only summer or winter conditions they are called single-use or mono-quality oils. To obtain multiple, more seasonal properties, conventional additives have to be added to different engine oil additives, ie SAE 5 base.

These additives will reduce the viscosity when the engine is running in colder conditions, but will also increase the viscosity at the engine operating temperatures. This product belongs to the category of universal lubricating oils and therefore has a great set of qualities.

5w30 oil is effective at a low temperature of -35° C (-31 F). Concerning the high temperature, it is 35 degrees C (95 F). Many manufacturers test their quality cars on special cabs. But, anyway, the characteristics that the manufacturer puts on the packaging can be significantly different from those that the substance will have during intensive work with the internal combustion engine.

In this regard, car dealers carry out their oil tests in working conditions. The tests are designed to show when the product loses its features.

What does 5w40 engine oil mean?

As I explained above the marks indicate how the oil is operating at high and low temperatures. In this manner, the 5w40 oil can operate at temperatures from – 35 degrees C (-31 F) to + 40º С (104 F).

To achieve a more economical ride, American engineers have introduced several parameters that give the right combination of certain SAE 5w40 viscosity oils that lead to energy savings. It is imperative to reduce oil consumption by 1.5%. In European practice (ACEA, ILSAC), this value exceeds a minimum value of 2.5%.

The main differences in SAE 5w40 quality:

  • High oxidation stability
  • Increased replacement interval
  • Oil stability
  • Engine cleaning properties

SAE 5w40 specifications and reviews:

  • Minimal engine contamination
  • Increased lifespan due to improved antioxidant properties
  • Reduction of friction in cold weather when the power unit is turned on
  • Evaporation resistance (savings on filling)
  • Reduces engine wear due to simple flow of SAE 5w40 synthetic oil at low temperatures

Due to this property, the engine will not run “dry” under freezing conditions, but the oil will get in all important components, and the engine’s service life will last. The thickness of the oil, first of all, depends on the size of this figure.

The difference between 5w30 and 5w40 engine oil types

The most noticeable difference between 5w30 and 5w40 is their viscosity at high temperatures.

5W30 at higher temperatures has a higher fluidity and a lower viscosity compared to 5w40. This means that it creates a thinner protective film on the engine parts than the 5W40 oil, which is thicker.

5W30 will be more liquid and 5W40 will be more viscous. At the same time, when starting the engine in winter, the oils behave the same, and the difference between these oils is negligible.

The working viscosity of 5w40 is 12.5 to 16.3 mm2 / s at 100 g, while at 5w30 the viscosity characteristic at high temperature is in the range of 9.3-12.6 mm² / s

Oil flow

5w40 ensures higher pressure, but less flow.

The thickness of 5w30 and 5w40

5W30 is lighter, so it has better fuel consumption.

Fuel economy

5w40 has a lower fuel economy.


5w30 can be used by different types of cars at different temperatures, but it is also ideal for colder temperatures. 5w40 is often used in cars whose engines have higher mileage and wear, which work better at higher temperatures, but also better than 5w30 at lower temperatures.


5w30 is usually more expensive.

5w30 or 5w40. What oil should I pick for my car?

Picking the right oil between those two types depends on a lot of aspects like driving style, the recommendation from the manufacturer, engine mileage, tolerance, and temperature-viscosity conditions

Although many manufacturers advise using the 5w40 oil type because of its universal beneficial properties, it is still advisable to use 5w30 oil on new engines that do not have high mileage at least until they reach a maximum of 100k km (approx. 63k miles).

After that, you can opt for 5W40, because the wear of the engine parts starts, and they require better protection due to the increased viscosity at operating temperatures.

5W40 is recommended for use on modern engines that run under heavy loads, many of which are equipped with turbos. It creates a reliable and sufficiently dense protective film, which ensures low friction, and prolongs the life of the engine, reducing the likelihood of a sudden failure.

Viscosity at low temperature (cP)5,0004,000
Viscosity at high temperature (cP)30,00040,000
Viscosity indexHigherLower
Cold weather performanceBetterGood
Hot weather performanceGoodBetter
Fuel economyBetterSlightly worse
Protection in extreme conditionsGoodExcellent

Note: Viscosity is a measure of an oil’s resistance to flow. It is commonly measured at two temperatures: low (usually -25°C) and high (usually 150°C).

The viscosity index (VI) is an indicator of how the oil’s viscosity changes with temperature. A higher VI means less change in viscosity with temperature changes.


The low-temperature characteristics of these lubricants are the same. Both products maintain optimum viscosity for cold engine start as well as good viscosity.

5w30 has a higher pumping power through the lubrication system. It cleans the engine parts much more efficiently, helps their cooling, and helps to save fuel.

But if the number of gaps in the friction couple increases, leaks may occur when using this oil and it’s better to change to 5w40 for higher protection of the engine.

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