Choosing the right lubricant is fundamental to the longevity of any internal combustion engine. The modern market offers such a variety of cans with multi-colored labels that an inexperienced driver can easily get lost in this ocean of characteristics. An incorrectly selected fluid can damage expensive components within a few kilometers, turning scheduled maintenance into a major overhaul.
In this article we will look in detail at what types of oils exist, how they differ in chemical composition and how to correctly read the labeling on the packaging. Understanding these nuances will help you avoid costly mistakes and extend the life of your car. We will not delve into the most complex chemical formulas, but will focus on the practical aspects that are really important to the car owner.
Ignoring the manufacturer's recommendations or blind faith in marketing slogans is a direct path to problems with the piston group and lubrication system. Motor oil not only performs the function of reducing friction, but also removes heat, cleans parts from carbon deposits and protects the metal from corrosion. That is why his choice should be approached as seriously and thoughtfully as possible.
Basic classification: mineral water, synthetic or semi-synthetic
All motor oils are divided into three main groups depending on the method of obtaining the base base. It is the base that determines the fundamental properties of the product, its stability at high temperatures and fluidity in the cold. The remaining components, including additives, only correct and improve these basic characteristics.
Mineral oils obtained by direct distillation of oil. This is the oldest and easiest to produce type of lubricant. Their main advantage is their low price and high penetrating ability, which allows them to wash out old deposits. However, they have a significant disadvantage: instability of properties at extreme temperatures. They thicken quickly in the cold and can burn when heated too much.
In contrast to them, synthetic oils are created by chemical synthesis from hydrocarbons. This allows engineers to “program” the properties of the liquid in advance: making it ideally fluid in cold weather and stable in hot weather. Synthetics have excellent cleaning ability and last much longer than their mineral counterparts, but are more expensive.
- 💧 Mineral oil is a product of direct petroleum refining, cheap, but short-lived.
- 🧪 Synthetic oil is the result of chemical synthesis, stable and expensive.
- ⚖️ Semi-synthetics - a mixture of basics, a compromise between price and quality.
⚠️ Attention: Never mix mineral oil with synthetic oil unless absolutely necessary. When different bases come into contact, a chemical reaction may occur, leading to sedimentation and loss of lubricating properties.
Semi-synthetic oils represent a compromise option. Usually it is a mixture of a synthetic base (about 20-30%) and a mineral base (the rest). This approach allows you to improve the characteristics of the mineral water while maintaining an affordable price. This is an excellent choice for engines with high mileage or for vehicles operating in moderate climates.
SAE viscosity: what do the numbers on the canister mean?
The most noticeable parameter for the buyer is the viscosity marking, e.g. 5W-30 or 10W-40. This classification was developed by the Society of Automotive Engineers (SAE) and tells how thick or thin an oil becomes at different temperatures. This parameter directly determines whether the lubricant can quickly reach the rubbing pairs during a cold start.
Number before letter W (from English Winter - winter) indicates low-temperature properties. The lower this number, the easier the oil turns the engine in cold weather. For example, 0W maintains fluidity down to -35°C, and 10W — up to -25°C. If you live in a region with harsh winters, you shouldn’t save on zero, since a cold start is 70% of engine wear.
The second number (after the hyphen) indicates the viscosity at engine operating temperature (about 100°C). Here the rule is the opposite: the higher the number, the thicker the protective film. For older engines with worn clearances, higher viscosity oils are often recommended (e.g. 40 or 50) to maintain system pressure. New engines with tighter clearances require thinner oils (20, 30), which are easier to pump through narrow channels.
Is it possible to pour oil of a different viscosity?
If you fill in 5W-40 oil instead of the recommended 5W-30, in hot weather the pressure may increase and the hydraulic lifters will begin to knock. If you fill in with 5W-20 instead of 5W-40, the film will become too thin for a worn motor, which will lead to a drop in pressure and possible rotation of the liners. A deviation of one step is usually acceptable as a last resort, but systematic changes in viscosity are not permitted.
Don’t think that “you can’t spoil porridge with butter.” Using too thick a lubricant in a modern engine can lead to oil starvation of the camshafts in the first seconds of operation, since the pump will not be able to quickly push the thick liquid through the system. Hydrodynamic resistance plays a critical role here.
When choosing a viscosity, always consider the climate of your region. For Siberia, 0W-30/40 is optimal, for the south of Russia - 5W-40/50, and for the middle zone, 5W-30 will be a universal option.
Chemical composition and API/ACEA standards
In addition to viscosity, it is critical to pay attention to tolerances and quality standards. Two main classification systems dominate the world: American API (American Petroleum Institute) and European ACEA (Association des Constructeurs Européens d'Automobiles). They determine the set of additives and the chemical compatibility of the oil with exhaust gas aftertreatment systems.
The API standard divides oils into two categories. For gasoline engines this category S (Service), followed by a letter indicating the generation of the standard (the further from the beginning of the alphabet, the more modern the oil). For example, SN or newest SP. The category is intended for diesel engines C (Commercial). Universal oils are double marked, for example, SN/CF.
The European ACEA standard is more stringent and takes into account the characteristics of European motors, which often operate at higher temperatures and loads than their American counterparts. Classes are important here A/B for passenger cars and C for engines with diesel particulate filters (DPF). Oil class C belong to the Low SAPS category - they contain a low amount of sulfate ash, phosphorus and sulfur, so as not to “strangle” expensive environmental systems.
| Standard | Engine type | Features | Application |
|---|---|---|---|
| API SP | Gasoline | LSPI protection, turbine compatible | Modern turbocharged engines |
| API CK-4 | Diesel | High oxidation resistance | Heavy equipment, trucks |
| ACEA A3/B4 | Gasoline/Diesel | High viscosity when heated | European cars without particulate filter |
| ACEA C3 | Gasoline/Diesel | Low SAPS (low ash content) | Cars with particulate filters and catalysts |
Ignoring ash content requirements can lead to rapid failure of the catalytic converter or clogging of the particulate filter. Repairing these components costs many times more than purchasing high-quality oil with the correct approval. Lubrication system must work in harmony with the exhaust system.
When buying oil for a car with a particulate filter (DPF/FAP), look for the Low SAPS or ACEA C class marking on the label. Otherwise, the filter will quickly fail.
Automobile Manufacturer Specifications: Why They Matter
You can often find logos of specific automakers on canisters: BMW Longlife, Mercedes-Benz MB-Approval, VW 504.00/507.00, Porsche A40. This is not just marketing, but the result of long-term testing of oil in specific engines. Automotive plant engineers are testing lubricant for waste, compatibility with rubber seals and impact on the environment.
The presence of a specific approval means that the vehicle manufacturer guarantees that the engine will operate as normal when using this product. For example, engines VAG groups are very sensitive to oil waste and require products with a certain additive package. Filling oil without approval VW 504.00 into modern TSI the engine can cause coking of the piston rings.
Where can I find information about the required permit? The most reliable source is the car’s service book or technical passport. Information can also be found on specialized resources for selecting oils by entering the VIN code of your car. You should not rely on the advice of “knowledgeable” garage neighbors if their recommendations contradict the manual.
- 🔍 Study the service book before purchasing.
- 🏭 Look for the car manufacturer's logo on the label.
- 📱 Use online selectors by VIN code.
There is a misconception that oil with approval Mercedes can't be poured into BMW. In fact, if the viscosity and basic parameters (for example, ACEA A3/B4) match, short-term topping up will not cause harm. However, for a planned replacement, it is better to strictly follow the recommendations of your car brand, since the requirements for antifriction properties may vary.
⚠️ Attention: If the instructions indicate a requirement for approval, but there is none on the canister, even if there are general API / ACEA standards, the use of such oil may void your engine warranty.
Transmission and hydraulic fluids
A car needs more than just motor oil. Transmission fluids operate under different conditions: they experience enormous pressure in the contact patch of the gears, but the temperature there is usually milder than in the engine. For manual transmissions (manual transmissions), extreme pressure properties are important, and for automatic transmissions (automatic transmissions), friction characteristics and viscosity stability are important.
Automatic transmissions use fluid ATF (Automatic Transmission Fluid). It performs a triple function: lubricates, cools and transmits torque to the torque converter. Classification Dexron (for GM, Toyota) and Mercon (for Ford) is key here. Mixing different types of ATF is strictly prohibited - this can lead to “kicks” when switching and destruction of the clutches.
For manual transmissions and rear axle gearboxes, oils marked GL (Gear Lubricant). Most common classes GL-4 and GL-5. Important to remember: GL-5 contains more sulfur additives that are aggressive to non-ferrous metals (copper, brass), which are often used in synchronizers for manual transmissions. Fill GL-5 in a box where required GL-4, can lead to rapid wear of the synchronizers.
☑️ Checking the oil level in the automatic transmission
Hydraulic fluid (in the power steering system) also requires attention. Often the same ATFs are recommended for power steering as for automatic transmissions, but there are systems that run on a special mineral fluid (for example, Pentosin). Mixing mineral water and synthetics in hydraulics will cause the rubber seals to swell and the rack to leak.
How often to change oil and how to avoid fakes
The issue of replacement frequency remains one of the most controversial. The regulatory 15,000 km specified by the manufacturer are relevant for ideal conditions: highway crossings at a constant speed. In a real city, with constant traffic jams and cold starts, oil ages much faster. Engine hours are a more accurate parameter than mileage.
The optimal interval for modern synthetic oils in urban conditions is considered to be 7,000 - 8,000 km. If you often get stuck in traffic jams, it is better to reduce the interval to 5,000 – 6,000 km. Oxidation products, accumulating in old oil, begin to corrode the liners and clog the oil channels.
Counterfeit remains a huge problem in the market. The most famous brands are counterfeited, so you need to buy oil only from official dealers or large chain stores that value their reputation. Pay attention to the quality of the canister: the seams must be even, the label must be glued evenly, the batch code on the bottom and on the neck must match.
- 📅 Change your oil at least once a year, even if you haven’t covered your mileage.
- 🛣️ In the city, reduce the replacement interval by 30-40% of the recommended one.
- 🔒 Check the security holograms and codes on the canister.
⚠️ Attention: Buying oil on tap or from dubious sellers on the market is a lottery with a high risk of buying waste or cheap mineral water with dye. Saving 500 rubles can cost a major engine overhaul.
Signs that it is time to change the oil ahead of time include its blackening (although this may be normal for diesel engines due to its detergent properties), the appearance of a burning smell, or a change in consistency (the oil has become too thin, like water). Check the level regularly with a dipstick and monitor the condition of the fluid.
Is it true that oil turns black due to poor quality?
No, often the opposite. If the oil remains light after 10 thousand km, this may mean that it contains few detergent additives and it does not clean the engine, but simply does not get dirty. Good oil “holds” dirt in itself until the next change, so it darkens.
The best maintenance strategy is to reduce replacement intervals. Frequent changes of inexpensive but high-quality oil are better for the engine than rare changes of “super-premium” oil.
Frequently asked questions (FAQ)
Is it possible to mix oils from different manufacturers if they are of the same viscosity?
A short-term top-up (up to 10% of volume) is usually acceptable in an emergency if the oils meet the same standards (for example, both API SN and ACEA A3/B4). However, bases and additive packages may vary between brands. During a scheduled replacement, it is better to completely drain the old oil or flush it to avoid chemical conflict between additives.
Is it necessary to flush the engine when switching from mineral water to synthetic?
Modern synthetic oils have high cleaning properties and will gradually clean the engine themselves. However, if you are switching from a mineral oil or an unknown oil, or there is visible deposits in the engine, it is recommended to use flushing oil or a “five-minute wash” before adding a new synthetic to wash away the sludge.
Is it true that synthetics leak through oil seals on old engines?
This is a myth. Synthetic oil does not “eat” rubber. The problem is that synthetics are more fluid (lower molecular weight). If the oil seals are already worn out and “stiff,” and mineral oil created a fat plug there due to its thickness and soot, then liquid synthetics will easily find its way out. Changing the oil has nothing to do with it - it's time to change the seals.
Which oil should I choose for an engine with high mileage (more than 200 thousand km)?
For engines with high mileage, it is often recommended to switch to a slightly more viscous oil (for example, from 30 to 40 according to the second SAE digit) or to use special “High Mileage” series. They contain conditioning additives that slightly swell rubber seals, preventing leaks, and have a reinforced package of anti-wear additives.