Frequently asked questions / Engine oils

How to choose the right engine oil for your car?

The choice of engine oil is made by the car manufacturer. The service documentation contains recommendations about the necessary requirements the engine oil should meet. These requirements concern the performance and viscosity parameters.

What is the recommended performance level?

The technical requirements engine oils must meet (or surpass) to provide an optimal performance in the engine are referred to as performance level. It is determined according to specifications, the most common of which are ACEA (European Automobile Manufacturers’ Association) and API (American Petroleum Institute).

What is АСЕА?

The АСЕА specification regulates the specific parameters and values which service-fill oils designed for engines of passenger cars, light commercial vehicles and large goods vehicles must meet.

How does АСЕА rate oils?

According to ACEA, oils fall into 3 major classes with relevant categories for each class and a designation of the year of implementation of the performance level:

A/B - Petrol and diesel engines of passenger cars and light commercial vehicles;

C – Catalyst compatible petrol and light duty diesel engines with exhaust after treatment devices: DPF and TWC / DPF - diesel particulate filter; TWC - three-way catalyst;

E - Heavy-duty diesel engines;

- The categories are designated by the number following the class: For example, C1, C2 ... A3/B3; A3/B4 ... E6, E7, etc.

- Year of implementation of the performance level: for example E5-02 ..., A3/B4-08, C1-10.

What is API and how does it categorize oils?

The American Petroleum Institute distinguishes two types of engines, denoted as "C" for diesel and "S" for petrol. The letters after "C" and "S" follow in an alphabetical order and correspond to the category development sequence: A, B, C, D, E, F ...

- Petrol - API: SA, SB, SC, SD, SE, SF, SG, SH (obsolete) and API: SJ, SL, SM, SN (current)

- Diesel - API: CA, CB, CC, CD, CD-II, CE, CF, CF-2, CF-4, CG-4 (obsolete) and CH-4, CI-4, CI-4 PLUS, CJ -4 (current)

What does the viscosity grade mean?

The viscosity grade (SAE) provides information on the viscosity-temperature properties of engine oils. These are defined by the kinematic or dynamic viscosity (or, in other words, the thickness of oil at different temperatures).

Are engine oils defined as “seasonal” according to their viscosity grade?

Yes, oils are classified as monograde and multigrade:

Monograde oils, depending on the season in which they are used, are summer oils (SAE 20, .. SAE 60) and winter oils (SAE 0W, ... SAE 20W), where W stands for the English word “winter”. Their use is climate-dependent and with the exception of very old vehicles with very high consumption rates, in modern cars it is ineffective and may even be dangerous.

Multigrade oils are designed for year-round operation. They are marked in the following way: SAE 0W-30 .. SAE 5W-40, ... 15W-50. The number before the letter "W" provides guidance on the low-temperature properties of the oil. The lower this number, the quicker oil flows at low temperatures and the easier it is to start the engine. The number after the letter W indicates the oil viscosity at 100°C.

This means that oil grades SAE 5W-40 and SAE 10W-40 have the same viscosity at 100°C, but their low-temperature properties are different.

Is it true that all SAE 10W-40 oils are identical?

NO, that’s not true! It is wrong to choose engine oil just by its viscosity grade.

SAE 10W-40, for example, indicates the low-temperature properties of oil and its kinematic viscosity at 100°C, but gives no information concerning its performance properties.

What is the colour of fresh oil?

The colour of fresh engine oil is not expressive of its quality since it depends on both the quantity and colour of components from which the oil is produced (base oils and additives).

Which brand and product line should I choose?

Every brand, such as PRISTA, TEXACO, etc., has developed its own product lines. The large product variety allows users to choose from a range of oils meeting different requirements according to the specific application. Oil product lines are specifically designed for passenger cars, light commercial vehicles, or large goods vehicles. For example, the HAVOLINE line of TEXACO is a range intended for light duty vehicles while URSA is for heavy duty diesel engines.

What is the optimal oil change interval?

Manufacturers of lubricants do not define mileage-based intervals. The operating conditions and vehicle maintenance intervals are specified by the equipment manufacturer in the service documentation which sets out the performance level and recommends a viscosity grade.

Are there any other criteria to determine a mileage-based oil change interval?

Yes, the optimum mileage is better defined by taking into account also other criteria such as:

- Engine run mode (normal or sport mode i.e. more intensive engine load);

- Driving conditions (rural, freeway or predominantly city driving (i.e. at short distances, with frequent engine starts / stops, and cold-start driving)

- Ambient dust level;

- Technical condition of car, year of manufacture and actual mileage per year;

Why do some labels give specifications for both gasoline and diesel engines?

This is because these oils are suitable for application in both gasoline and diesel engines, and are particularly fit for use in mixed vehicle fleets.


The choice of a motor oil for a certain type of engine is a personal decision that is not determined by the price or brand of a product but by the correct interpretation of the manufacturer’s requirements and the technical condition of the vehicle.