What does 10w40 engine oil mean and when to use it

In the automotive world, 10w40 is known as the oil that helps the engine with many miles.

Although there is a very wide range on the engine oil market, each oil has different specifications, with very few similarities and quite a few differences.

Just as there are many types of engines, inevitably the range of oils is varied, to provide good performance to all engines.

In its composition, the 10w means what viscosity/flow the oil has at low temperatures, and 40 means what viscosity the oil has at high temperatures, the thinner the number, the lower the viscosity, and the w letter means winter

Which engine uses the 10w40 oil?

First of all, 10w40 engine oil is used in cars where the manufacturer specifies the use of this oil. Check your car manual for instructions regarding the correct oil to use in your engine. Also, 10w40 is a perfect oil to use in an engine with high mileage, because of the benefits it can offer.

According to the SAE standards, 10w40 can be used at temperatures not lower than -25 degrees Celsius (-13 degrees Fahrenheit) according the 10, and the 40 as I said above is the viscosity of the engine at high temperatures (maximum temperature of +40 degrees Celsius, +104 degrees Fahrenheit).

Being quite a thick engine oil, 10w40 can be used on engines where oil channels are wide open. If this is the case then you should be careful because the use of other types of engine oil can be harmful to your engine, because of worn piston rings and damage to other parts because of oil starvation.

Engines with high mileage, starting from approximately 70000 miles, parts are beginning to wear, increase gaps form between the connected parts. Thus, a thicker lubricating oil film is required for a sufficient level of lubrication, which is better provided by the 10W40 oil.

That’s why it is better to use this oil in an engine with high mileage, it ensures its long-term operation by extending its service life.

What to look for when choosing the 10w40 oil for your engine?

Engine oils have a lot of properties and they can be overwhelming for a person that does not understand much of those properties. The best guide you can have when choosing your engine oil is your car’s user manual. You will find there detailed information about what oil your engine needs.

Of course, most of the manufacturers advise you to use their brand, but the oil market is very diverse that sometimes it can be overwhelming.

For a good 10w40 engine oil it’s always better to consider the following:

  • Anti-corrosion properties. This feature is very important, a good 10w04 oil should not have additives that cause chemical corrosion because these additives can damage materials under their influence, and should not cause rust spots on the metal parts of the engine
  • Protective and cleaning properties. All engine oils should have these by default, but oils are very different in quality. Good 10w40 oil should have additives that clean the engine parts from deposits and tar and also, the oil should protect against all engine operating conditions such as high temperatures, low temperatures, use of low-quality fuel, and so on.
  • The oil should be ACEA, SAE, and API compliant. The manufacturer indicates the classes that engine oil corresponds to, according to the specified standards. Make sure these classes are the same as in your car’s manual. You can read more detailed information about these classes and standards in the article I wrote about engine oil properties
  • Brand and prices. There are more oil brands than we think and, of course, they have different prices. Some prices for the same oil brand with the same properties can vary a lot. Prices also depend on additives, if the oil is synthetic, semi-synthetic, or mineral, quality, and so on. The best oil you can buy is not the one with the highest price, but the one that your engine is comfortable with.
  • Resistance to temperature changes. If we talk about the 10w40 oil, a quality one should not freeze at temperatures above -25 C (- 13 F), and at high temperatures, it should have the viscosity described by the manufacturer.
  • Fuel economy. The certain amount of friction that the oil provides in the engine affects the level of fuel consumption
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