Important Terms from A to Z

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Engine Oils / Motor Oils (Monograde Oils, Multigrade Oils, Low Viscosity Engine Oils, Semi-Synthetic Engine Oils, Synthetic Engine Oils)

Engine oils are lubricants that are used in combustion engines. Their most important property is lubricity, i.e. how well they minimize the friction of the mechanical components in an engine under the conditions prevailing in the engine. Engine oils are divided into classes according to specific properties – an engine oil’s quality traits are based on factors such as friction reduction, compatibility with sealing materials, cleaning effect and oil sludge prevention. Depending on their type, motor oils are produced either from petroleum, i.e. base oils from crude distillation, or from a blend of petroleum and synthetic base oils (= semi-synthetic motor oils), or from purely synthetic base oils/base oils not resulting from crude distillation (= synthetic motor oils). Nowadays almost all motor oils are alloyed motor oils, i.e. additives are added to them (up to 20%) to improve their properties, including aging resistance, corrosion properties, friction properties, wear reduction and viscosity index.

Viscosity of engine oil and SAE classification

The Society of Automotive Engineers (www.sae.org) defines the SAE classes based on the most important property of engine oils: their viscosity, i.e. the measure of friction of the engine oil. Depending on the reference temperature, the viscosity of engine oils, i.e. thin or thick fluid (and consequently their flow behavior) changes. So the ambient / outside temperature (summer / winter) also plays a role in motor oil, though motor oils are nowadays usually no longer offered as summer oils and winter oils (only for certain applications such as racing), but as multigrade oils that combine the properties of summer and winter oils. Multigrade oils are indicated in their classification SAE J300 in a combination of numbers: In the case of the engine oil with the designation SAE 0W-40, for example 

  • the "W" is winterized, 
  • the number "0" in front of the W indicates the engine oil’s flow properties at low temperatures (from 0 = thin to 25 = thick), i.e. how quickly it can reach individual components in the engine at low temperatures (low-temperature viscosity),
  • the number 40 at the end describes the oil’s behavior at a temperature of 100°C (high-temperature viscosity).

Special additives are added to multigrade oils (also called VI improvers with reference to the viscosity index VI), so that the viscosity increases at higher temperatures for an independence of temperature that did not exist before. Until the 1970s, monograde oils were the standard in engines. The disadvantage of multigrade oils is that the higher the proportion of certain additives (polymers), the faster the engine oil ages in operation, which is why traditional monograde oils are still used in motor sports, for example. Since synthetic motor oils have been around, however, this problem has become less and less of a priority, as modern fuel-efficient engine oils are not only fuel-efficient but also offer ever longer change intervals thanks to their advantageous properties. These low-viscosity engine oils are combined with high-quality additives - virtually all multigrade oils with the numbers 0W or 5W are synthetic or semi-synthetic low-viscosity engine oils and can save fuel with the appropriate engine technology – but only if the vehicle manufacturer has approved these engine oils for the vehicle type. Longlife engine oils are synthetic fuel-efficient engine oils for vehicles with computer-controlled Longlife service intervals. They must not be mixed with other engine oils in order to comply with the longer change intervals that the engine control unit detects when it is set to Longlife service.

It is important that only the engine oil that has been approved for each vehicle type according to the manufacturer's specifications is used. In this way, vehicle damage is avoided and guarantee and goodwill claims do not expire. Which engine oil a vehicle can tolerate or which engine oil is recommended can generally be found in the operating instructions of the vehicles. The vehicle dealer can also be consulted to find out the type of engine oil required.

Performance classifications of engine oils: API, ACEA, manufacturer-specific standards

The American Petroleum Institute (www.api.org) provides the specifications of the API classifications (American requirements and quality criteria); the European Automobile Manufacturers Association (Association des Constructeurs Européens d'Automobiles, www.acea.be) issues the ACEA specifications, which define the European requirements for engines and driving conditions. ACEA replaces the former CCMC classifications. Engine test runs are carried out in the laboratory to arrive at the classification of engine oils.

ACEA classifications:

  • A = Engine oil for passenger car gasoline / petrol engines
  • B = Engine oil for diesel engines in passenger cars, vans, and small transporters
  • C = Engine oil for gasoline / petrol engines and diesel engines with new exhaust gas aftertreatment systems (e.g. soot particle filters)
  • E = Engine oil for truck diesel engines and commercial vehicles

Automobile manufacturers additionally create requirement profiles by testing the engine oils in their vehicle types themselves. These are defined in company-specific standards such as VW 502 00, BMW LL-98, Porsche A40 etc. and should be observed without fail.

Motorcycle oils

There are basically few differences between car-engine oils and motorcycle-engine oils. However, since almost all motorcycles have a combined gearbox and engine, i.e. there is only one oil circuit and the piston speed is significantly higher, the requirements for motor oils for two-wheelers are higher than for passenger cars. Due to the higher pressure load, special high-pressure/EP additives are added. These are present only in small quantities, if at all, in passenger-car engine oils.

Also, no additives may be used to reduce the coefficient of friction in motorcycles with wet clutches, where the gears run in the engine’s oil bath. Here, only premium oils should be used that are explicitly named by the manufacturer.

Engine oils and lubricants are traded through the Mabanaft Group and its subsidiaries: OIL! service stations offer motor oils and lubricants at their filling stations. In the retail sector, lubricants are also distributed through Petronord companies.

Status: January 2020
All information subject to change. Errors and omissions excepted.

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