The choice of engine oil is wide, but not all vehicles can withstand every type of oil. This guide is intended to provide all the important information for purchasing an engine oil: from information on the packaging, such as specifications and codes, to the necessary basic notions of engine oil and engine care.
What are the functions of engine oil?
Before we delve into the subject, we would like to briefly explain the various tasks of your engine oil.
Lubrication: This is the most important task of the engine oil: through a continuous action of the oil, the friction between 2 metal surfaces must be kept as low as possible.
Cooling: Internal combustion engines generate a lot of heat and this must be dissipated. Oil can absorb this heat energy and release it again through an oil pan or extra oil cooler.
Watertightness: The sealing rings between the sliding parts (bearings, pistons, camshafts, and crankshafts). This prevents pressure from escaping at the transitions between housing and shafts and the car does not lose power.
Cleaning: During combustion, a lot of combustion residues are produced on the piston wall. The oil absorbs the residues and transports them to the oil filter. This keeps the engine clean inside and reduces fuel consumption and polluting emissions.
Corrosion Protection: Oil protects bare metal surfaces from corrosion
Noise reduction: Thanks to the oil film and sliding properties of the surfaces, the oil also serves to reduce engine noise
If you need to change the engine oil and you are in the middle of the road, you call for towing services.
Why is the engine oil changed?
Engine oil is exposed to a great variety of stresses and strains and therefore needs to be changed after a certain period of time. What are the loads involved?
Blow-by-Gase: Despite the tightness, the combustion gases can pass through the cylinder wall and enter the crankcase, where they are bound in the oil.
Oil degradation: in internal combustion engines, during the cold start phase, it can happen that fuel as well as gases enter the oil and adversely affect lubrication.
Oil thickening: Especially in diesel engines, a lot of soot particles get into the oil, which can also thicken due to the permanent additive.
Mechanical Loads: Engine oil must be able to withstand high loads. This means that the long molecules are literally torn apart and the thickening of the oil is at risk. High shear stresses are present, for example, in the piston ring area (high speeds, sliding speeds, pressures, and temperatures).
Thermal loads: The oil is exposed to different temperatures in different places in the engine, for example, it is much hotter at the pistons than in the oil pan or in an oil cooler.
Condensing water: If you travel very short distances in winter, a yellowish burr may form on the oil filler cap which indicates the presence of condensed water. However, after a long trip, this formation disappears again due to the correct operating temperatures.
Where can I find information on the oil my vehicle needs?
First of all, you can take a look at your car’s manual or service booklet. In Norway, with its coldest winters, the motor oil has different needs than in Italy, which is getting hotter. Of course, you can also find what you are looking for by entering your vehicle details online.
What do the different codes, letters, and numbers mean?
Each vehicle manufacturer has their own requirements for the right engine oil for their models, so-called manufacturer approvals. The oils are also classified according to viscosity classes in order to be able to compare motor oils from different manufacturers.
The viscosity of the engine oil is indicated by the SAE viscosity classes, e.g. SAE 5W30, 5W40, 10W40. Which SAEs your vehicle needs are indicated in the user and maintenance manual. Technically, the various oils are also differentiated according to the ACEA, API, and ILSAC classes.
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What is an SAE viscosity grade?
SAE is short for “Society of Automotive Engineers”. The organization defines technical standards for the automotive industry, including viscosity classes.
What are the ACEA specifications?
In the European ACEA classification, the engine and vehicle types for which the respective engine oil is intended are identified by letters
Where can I see which oil my vehicle needs?
In the owner’s manual and in the maintenance booklet of the car.
What are the functions of engine oil?
Engine oil is used for lubrication, cooling, fine sealing, cleaning, corrosion protection and sound insulation.
Why change the engine oil?
Engine oil is consumed, among other things, by combustion residues.
What is the risk of the wrong oil for my car?
If the oil is too thick or too thin, the lubrication function is not working optimally. In the worst case, there is a risk of engine damage.
What happens if you fill too much oil in the engine?
Engine seals risk leaking or forming air bubbles in the oil. In the worst case, in addition to leaking at faulty seals, oil can also be drawn into the engine and burn there. The result is engine damage.