Meaning of Marking of Engine Oils

Purchase of high-quality motor oil for your car guarantees safe operation of transport over a long period of time. It is worth to observe the replacement interval of fluids and not fill the engine with oil, that don't correspond to a season or engine type.

In order to distinguish necessary oils, you should understand such question as marking of engine oils. Often the driver doesn't understand anything in the meaning of these digits, indexes and letters. You need to insure yourself and the car from use of low-quality or improper engine oil.

What can oil marking tell the driver?

On the canister marking with engine oil can be found seasonal accessory of a product, its temperature indexes, viscosity index and other characteristics which will help to choose perfect oil for the car.

The most important factor of marking is the oil type - for the petrol or diesel engine. Often this information is specified without marking in English. But American oils may use letters S (oil for gasoline powertrains), C (for diesel engines of trucks) and S/C (the universal oils).

Also on marking it is possible to distinguish the following properties of seasonal accessory:

  • oils with figure at the end of an index and without letter W in designation - summer options;
  • all oils with a letter W on the marking end - winter one;
  • oils all-weather are marked with a letter W in the middle and figure at the end.

This classification is according the international SAE standard. It makes it very easy to understand how oil marking is decoded. Letters at the beginning of marking indicate classification type. In our case it is SAE. Followed by  the figure denoting viscosity, or a letter W with denoting of seasonal accessory.

Oil viscosity increases with numerical value in marking. If the product of SAE 15W40 is standard using in many import petrol engines, 15W50 pour into worn-out force aggregates with big mileage.

Choosing the temperature and oil viscosity

It is important not only to know what do the figures in oil marking mean, but also to understand a right choice of the necessary oil for your car. The all-weather oils are most popular, after all  not every car rides a mileage of service interval during one season.

But winter oils are useful in northern part of the world where without using oil with the under temperature index it is impossible to have even the most reliable car to winter time. The temperature index is denoted by figure in the middle of marking before a letter W. Indexes represent the following meanings:

  • the zero index indicates the maximum resistance of oil to frosts;
  • digits 5 and 10 make it easy to start the engine at ambient temperature to-25 degrees;
  • the index 20 allows to start a car without problems to air temperature of-10 degrees.

Oil viscosity is chosen for other parameters. Marking of the modern synthetic engine oil by this criterion is described above. It is possible to choose the necessary oil viscosity for car run. After passing of a mark to 200 thousand kilometers it is possible to stop fulfilling manufacturer requirements and use more viscous oil for creation of the necessary pressure in lubrication system. It will help to prolong considerably life of the engine and to provide its normal functioning.

It is impossible to give specific advises at the choice of viscosity. Only expert can define optimum viscosity of engine oil only in professional inspection service station. Own decisions areoften precipitate and can harm your car.

Summing up

Marking of motor oil for gasoline engines is no different from other types of lubricant.This fact causes considerable controversy among drivers who believe that almost became a dupe in the auto shop.

Now you know the basic criteria of marking engine oil in SAE system. Also you can meet on the marking label oils according to API. This American system of quality evaluation, which we discussed above. Whatmotoroil doyouuse?

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CarAraC Research

About the authors

The CarAraC research team is composed of seasoned auto mechanics and automotive industry professionals, including individuals with advanced degrees and certifications in their field. Our team members boast prestigious credentials, reflecting their extensive knowledge and skills. These qualifications include: IMI: Institute of the Motor Industry, ASE-Certified Master Automobile Technicians; Coventry University, Graduate of MA in Automotive Journalism; Politecnico di Torino, Italy, MS Automotive Engineering; Ss. Cyril and Methodius University in Skopje, Mechanical University in Skopje; TOC Automotive College; DHA Suffa University, Department of Mechanical Engineering

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