What goes into a car engine: a complete guide to liquids and oils

The engine is the heart of the car, and what you put into it determines its durability, power and even fuel consumption. Many car owners mistakenly think that simply changing the oil on time is enough, but in fact, a whole complex of liquids gets into the engine: from fuel and antifreeze to specialized additives. A mistake in choosing at least one of them can result in expensive repairs.

In this article we will look at all types of liquids, which are poured into the engine, their functions, selection criteria and consequences of improper use. You will learn how different synthetic oil from semi-synthetics, why you can’t mix antifreezes of different colors, and what happens if you fill a gasoline engine with diesel fuel. We will also provide a checklist for checking fluid levels yourself and answer frequently asked questions.

The material will be useful both for beginners who are just learning the basics of car ownership, and for experienced drivers who want to systematize their knowledge. All recommendations are based on manufacturer standards (API, ACEA, SAE) and experience of service centers.

1. Motor oil: the basis of engine health

Motor oil is the only fluid that constantly circulates in the engine under pressure, protecting its parts from wear, overheating and corrosion. Its main functions:

• 🛡️ Lubrication rubbing surfaces (pistons, crankshaft, camshaft).
• 🔥 Cooling — removes up to 40% of heat from heated parts.
• 🧹 Cleaning — keeps combustion products and metal shavings in suspension.
• 🔇 Sealing — fills microgaps between rings and cylinders, increasing compression.

There are three types of oils on the market:

• 🧪 Mineral - cheap, but quickly loses its properties. Suitable for older vehicles with large gaps.
• ⚗️ Semi-synthetic - compromise on price and quality. Optimal for most gasoline engines.
• 🔬 Synthetic - the most stable, withstands extreme temperatures. Recommended for turbocharged and diesel engines.

Key parameters when choosing:

• SAE 5W-30 - viscosity (the first number is responsible for cold start, the second - for operation at high temperatures).
• API SN or ACEA C3 — quality standards (the higher the letter after S or C, the more modern the oil).
• 🚗 Compatible with engine type (gasoline/diesel/hybrid).

⚠️ Attention: If the car manual states API SP, and you fill API SL, the risk of deposits forming on the valves increases 3 times. This is critical for engines with a system VVT-i or MultiAir.

2. Antifreeze and antifreeze: why you can’t fill it with water

The engine cooling system operates at antifreeze - a liquid that does not freeze at sub-zero temperatures and does not boil when overheated. Many people call it “antifreeze” in the old fashioned way, but this outdated name domestic antifreeze, which today is used only for oils in Soviet cars (for example, VAZ-2106 or Moskvich-412).

Modern antifreezes are divided into three types according to production technology:

Type	Color	Service life	Compatibility
G11	Green/blue	2–3 years	Old cars, cast iron blocks
G12	Red/orange	5 years	Modern gasoline internal combustion engines
G13	Purple/pink	Lifetime*	Turbocharged, hybrid engines

* - provided there are no leaks and no dilution.

Main mistakes when working with antifreeze:

• 🚫 Mixing different colors leads to sedimentation and clogging of the radiator.
• 🚫 Dilution with water by more than 20% reduces the boiling point to +100°C (risk of overheating).
• 🚫 Using expired antifreeze loses its anti-corrosion properties.

3. Fuel: gasoline, diesel and alternative types

Fuel is not just a “fuel”, but a complex chemical mixture, the quality of which determines engine life, acceleration dynamics and even the environmental class of the car. The most common in Russia are:

• ⛽ AI-92 - a budget option for old carburetor engines.
• ⛽ AI-95 - standard for most fuel-injected cars.
• ⛽ AI-98 — premium fuel for turbocharged and sports internal combustion engines.
• ☣️ Diesel (DT) — for diesel engines (it is important to pay attention to seasonality: summer/winter/arctic).

What happens if you fill with the wrong fuel?

• 🔥 Gasoline to diesel engine — there is no lubrication of the fuel system, the high-pressure pump fails within 50–100 km.
• ⚡ Diesel to gasoline engine — the injectors become clogged, the spark plugs become covered with soot, and compression drops.
• ❄️ Summer diesel fuel in winter — fuel waxes at –10°C, filters become clogged, the engine stalls.

⚠️ Attention: If you accidentally fill in the wrong fuel, don't start the engine. Drain the tank and flush the system - it’s cheaper than repairing fuel equipment (from 20,000 ₽).

Alternative fuels:

• ⚡ Gas (methane/propane) - 40–50% cheaper than gasoline, but requires the installation of gas equipment (from 35,000 ₽).
• 🌱 Biofuel - environmentally friendly, but rarely found at gas stations and can damage rubber seals.
• ⚡ Electricity — for hybrids and electric cars (does not apply to traditional internal combustion engines).

How to check the quality of gasoline at a gas station?

Dip a clean piece of paper into the fuel for 5 seconds. If after drying there are greasy stains or sediment left, there are impurities in the gasoline. You can also use rapid tests (available at auto parts stores) that change color in the presence of water or resins.

4. Additives and flushes: when you really need them

Additives are auxiliary compounds that are added to oil or fuel to improve their properties. They are divided into several categories:

Additive type	Purpose	When to use
Anti-friction	Reduce friction, reduce wear	For older engines with high mileage
Cleansing	Dissolves carbon deposits and deposits	Before changing the oil or after buying a used car
Restorative	Restore metal surfaces	If microcracks or burrs are detected
For turbine	Prevents oil coking	Mandatory for turbocharged internal combustion engines

Engine flushes are used before oil changes to remove sludge and deposits. They are:

• 🧴 Soft - added to old oil 200–300 km before changing.
• 💦 Liquid — fill in instead of oil, the engine runs for 10–15 minutes at idle.
• ⚠️ Aggressive - used only in services, they can damage the seals.

⚠️ Attention: Additives are not a panacea. If the engine is already worn out (knock of liners, low compression), they only temporarily mask the problem. In 80% of cases, major repairs are required.

Fill only if there is a specific problem (knocking, smoke, increased oil consumption)|Do not mix additives from different manufacturers|Follow the dosage (usually 50–100 ml per 4–5 liters of oil)|Rinse the engine after using aggressive compounds-->

5. How to check fluid levels yourself

Regular monitoring of oil, antifreeze and brake fluid levels is basic procedurewhich every car owner should be able to perform. It is enough to devote 5 minutes to this once a month to avoid serious damage.

Oil check:

1. Place the car on a level surface, turn off the engine and wait 10 minutes (the oil should drain into the crankcase).
2. Remove the oil dipstick (usually marked with a yellow or orange handle) and wipe it with a clean cloth.
3. Insert the dipstick back all the way and remove it again. The level should be between the marks MIN and MAX.
4. Assess the condition of the oil: if it is black, has metal shavings, or smells like burning, it needs to be replaced urgently.

Antifreeze check:

• Open the hood and locate the expansion tank (a clear plastic reservoir containing colored fluid).
• The level should be between MIN and MAX. If there is not enough antifreeze, add more same composition, which is already filled.
• Check if there is any turbidity or flakes in the reservoir - this is a sign that it is time to change the fluid.

Checking the brake fluid:

• The reservoir is usually located near the master cylinder (under the hood on the driver's side).
• The liquid should be light yellow or clear. If it is dark, replacement is required.
• The level should be close to MAX. A drop in level may indicate a leak.

6. Common mistakes and their consequences

Even experienced drivers sometimes make mistakes when servicing the engine. Here are the most common of them and what they threaten:

• 🛢️ Oil overflow — leads to foaming, increased pressure and squeezing out the seals. Normal: the level should be strictly between MIN and MAX.
• 🔄 Mixing oils of different brands - even if the viscosity is the same, the additives can react and form a deposit.
• ❄️ Using water instead of antifreeze - in winter this is a guaranteed rupture of the cylinder block, in summer - corrosion and overheating.
• ⏳ Missing the oil change date — after 15,000 km (or a year), the oil loses its properties, and accelerated engine wear begins.
• 🚗 Ignoring "check engine" - even if the engine is running normally, the error may indicate problems with the fuel system or ignition.

Case Study: Owner Toyota Camry 2015 poured into the engine 5W-40 instead of recommended 0W-20. After 20,000 km, a knocking sound from the hydraulic compensators appeared, and diagnostics showed clogged oil channels. The repair cost 45,000 rubles.

Another typical situation is saving on antifreeze. Driver Renault Duster diluted G12 water by 50%, after which in the summer on the highway the engine overheated and the cylinder head began to wobble. The restoration cost 80,000 rubles.

7. How to choose fluids for a specific car

There are no universal recommendations - the choice depends on car models, engine type and operating conditions. Here is the selection algorithm:

1. Read the instruction manual — oil tolerances are indicated there (for example, VW 502.00 for Volkswagen) and type of antifreeze.
2. Consider the climate:
   • For northern regions - low viscosity oil (0W-20, 5W-30).
   • For hot climates - high viscosity (10W-40, 15W-50).

Focus on mileage:

• Up to 100,000 km - synthetics with low ash content (Low SAPS).
• 100,000–200,000 km - semi-synthetic with anti-friction additives.
• Over 200,000 km - oil with a high content of detergent additives (High Detergent).
• Check compatibility - use online selection services (for example, Mobil Oil Selector or Liqui Moly Advisor).

Examples for popular models:

• Lada Vesta — 5W-40 (Rosneft Magnum or Lukoil Luxe), antifreeze G12+.
• Kia Rio — 5W-30 (Shell Helix Ultra), antifreeze G12++ (purple).
• BMW 5 Series (F10) — 0W-30 (Castrol Edge), antifreeze G13.
• Toyota RAV4 (hybrid) — 0W-16 (Toyota Genuine Motor Oil), antifreeze Super Long Life.

FAQ: Answers to frequently asked questions

Is it possible to mix 5W-30 and 5W-40 oil?

In emergency cases (for example, on the highway), you can mix oils one manufacturer with the same quality standard (API/ACEA). However, after this, it is recommended to change the oil and flush the engine as soon as possible. Prolonged use of the mixture will lead to deterioration in lubricating properties and the risk of deposits.

What happens if you don't change antifreeze for 5 years?

Aging of antifreeze leads to:

• Loss of anti-corrosion properties - rust corrodes the radiator and pump.
• Reduced heat transfer - the engine begins to overheat.
• Formation of sediment - the channels of the cooling system become clogged.

For most antifreezes (G11, G12) maximum service life is 3–5 years. G13 may last longer, but requires level and condition monitoring.

What kind of gasoline should I put in a turbocharged engine?

For turbocharged engines (TFSI, T-GDI, EcoBoost) gasoline with octane rating is recommended not lower than 98. This is due to:

• Increased compression ratio (risk of detonation on 92nd gasoline).
• Sensitivity of the turbine to fuel quality (carbon deposits on the blades).
• Manufacturer's requirements (for example, Audi and BMW will void the warranty if you use the 95).

If 98 is not available, short-term use of 95 with octane-boosting additives (for example, Liqui Moly Octane Plus).

Do I need to flush the engine when changing the oil?

Flushing is required in the following cases:

• When switching from mineral oil to synthetic oil.
• After purchasing a used car (it is unknown what the previous owner filled in).
• If the old oil is heavily contaminated (black, with metal shavings).

For new cars (up to 100,000 km), flushing is not required if the oil has been changed regularly.

Is it possible to put diesel oil into a gasoline engine?

Diesel oil (API CJ-4, ACEA E9) has a higher base number and ash content, which is necessary to neutralize sulfur in diesel fuel. The oil in a gasoline engine is:

• Rapidly forms deposits on pistons and valves.
• May cause ring sticking (due to excess additives).
• Reduces catalyst life (due to high ash content).

An exception is universal oils marked API SN/CF, which are suitable for both types of engines.