The situation of gasoline entering the crankcase and mixing with engine oil is one of the most serious malfunctions that an owner of a car or outboard motor can face. Ignoring the first symptoms of this problem inevitably leads to a decrease in the viscosity of the lubricant, which causes accelerated wear of rubbing vapors, overheating and, ultimately, overhaul of the power unit. Understanding the physics of the process and timely identification of the causes of fuel leaks avoid costly recovery of equipment.
Often drivers notice changes in engine behavior too late, when the oil level on the probe has already exceeded the maximum mark and the smell of fuel is clearly audible. However, there are earlier signs that should be considered in daily operation. In this article, we will look at the mechanics of the process, diagnose malfunctions and determine the algorithm of actions to eliminate the fuel entering the lubrication system.
The main symptoms and signs of oil thinning
The first and most obvious sign that petrol hits oilThe liquid on the probe becomes too liquid, loses its characteristic oiliness and acquires a sharp smell of fuel. If you notice that the oil level inexplicably increases, and the color becomes lighter and more cloudy, this is a direct signal that you need an immediate diagnosis.
The engine also starts to behave differently, and because of the reduced lubrication properties of the mixture, there may be a foreign noise, a knock or a hum, especially when starting cold, the engine oil, saturated with fuel, is not able to create the necessary protective film on the parts of the cylinder-piston group, which leads to friction of metal against metal.
In addition, the following indirect symptoms may occur:
- 📉 Falling oil pressure on the dashboard, as the diluted mixture is easier to pump through the system.
- 💨 Increased fuel consumptionThis is not due to driving style or changing road conditions.
- 🌡️ Overheating of the engine due to a violation of heat sink and changes in the specifications of the lubricant.
⚠️ Warning: If you smell gasoline from the oil filler neck with the hood open, do not start the engine again until you find out the reasons.
Fuel penetration mechanism into the crankcase
In a proper internal combustion engine, fuel and oil are separated by pistons and osteoils, but when leakage or control failures occur, gasoline can leak into the crankcase, most often through gaps between the piston rings and cylinder walls, especially when the engine is in enriched mix mode.
The mixing process is exacerbated by frequent short trips when the engine does not have time to warm up to operating temperature, in which some of the fuel does not burn and flows down the cylinder walls into the crankcase, a phenomenon especially characteristic of modern direct injection engines, where the pressure in the fuel ramp is very high.
The condition of the crankcase ventilation system also plays an important role: if the PCV valve jams or does not work correctly, an excess pressure or vacuum is created in the crankcase, which can contribute to the fuel sucking through leaky seals. Oil dilution This is happening gradually but steadily.
In diesel engines, especially those equipped with particulate filter regeneration (DPF), fuel can enter the oil during the burn procedure. If the process is interrupted or occurs too often, unburned diesel fuel drains into the pallet, mixing with the lubricant.
Failures in the ignition and mixture system
One of the key reasons gasoline gets into the oil is ignition failures, and when the spark on the candle is missing or too weak, the fuel-air mixture in the cylinder does not ignite, and as a result, liquid gasoline flows down the walls of the cylinder directly into the oil pallet, a phenomenon called "pot-ignition" or simply ignition skipping.
Defective spark plugs, high-voltage wires or ignition coils are the first candidates for testing. If even one cylinder is unstable, the combustion efficiency drops, and the amount of unburned fuel entering the crankcase increases. injector Continues to spray fuel into a non-functioning cylinder.
You also need to pay attention to the fuel injectors, and if the injector is pouring (not keeping the pressure closed) or if the spray torch is broken, the fuel is supplied in excess, and the excess gasoline does not have time to burn, and the oil film is washed off the cylinder walls, and then it is in the crankcase.
Diagnosis requires checking the condition of the candles, black or wet, gasoline-smelling candles will indicate problems with a particular cylinder, and regular replacement of candles and filters is a basic prevention of this problem.
Pressurization problems and mechanical damage
Mechanical damage to engine components is a more serious category of causes: the wear of piston rings causes them to stop fitting tightly to the cylinder walls; through the gaps, gases and fuel break into the crankcase; this is a natural aging process of the engine, but it can be accelerated by overheating or using poor-quality fuel.
Deformation of the cylinder head or a breakdown of the gasket of the HBC can also lead to the entry of fuel into the oil, although more often this leads to the introduction of antifreeze. However, in some motor designs, the violation of the geometry of the HBC affects the valves, causing them to close tightly and, as a result, fuel dumping.
Special attention should be paid to the aperture of the gas pump in the engines with mechanical drive of the fuel pump. If the aperture is disturbed, the gasoline under pressure will directly enter the crankcase of the engine, which is one of the most dangerous situations, since the oil level can rise critically quickly.
How to check the diaphragm of the gas pump?
Remove the fuel pump and inspect the diaphragm for cracks, and you can temporarily shut off the fuel supply and start the engine on the residues in the carburetor — if the oil level stops rising, the problem is the pump.
Diagnosis and methods of checking the condition of oil
To accurately determine the presence of gasoline in oil, it is not enough just to look at the probe. Professional diagnostics involves several stages. First of all, a visual and tactile examination is performed. A drop of oil applied to white paper, when there is gasoline, forms a wide transparent ring around the dark spot of sediment.
A more accurate method is to test the oil in the laboratory or use testers to measure the flash point of the oil. Gasoline significantly reduces the flash point of the lubricant. If the oil flares up below 100°C (instead of the standard 200-220°C), the fuel content is high.
It is also useful to conduct a viscosity comparison: a drop of pure oil spreads more slowly than a diluted mixture; at home, you can drop oil on a hot surface (for example, a heated engine cover), but you need to do this extremely carefully.
| Parameter | Norma. | Sign of gasoline hitting |
|---|---|---|
| Smell. | Specific oily | The sharp smell of fuel |
| Viscosity | Tall, squishy. | Liquid, (like water) |
| Level on the probe | Stable. | Exceeds maximum (MAX) |
| Colour | Dark brown/Black | Lighter than usual, murky |
⚠️ Warning: Do not use fuel-marked motor oil to lubricate other machinery, even temporarily. It has lost its properties.
Effects of operating an engine with fuel in oil
Operating a diluted oil engine is a direct route to failure, reducing the viscosity of the oil pump can not create the necessary pressure in the system, as a result of which parts operating in hydrodynamic friction mode (knee, camshaft, piston fingers) are left without lubrication.
The first to suffer is the turbocharger, if it's installed. The turbine spins at a tremendous speed and requires perfect lubrication. The ingress of gasoline into the oil causes the turbine bearings to coking and the shaft to wear out quickly. Repairing the turbine is often more expensive than replacing the oil and filters.
In addition, gasoline is aggressive against rubber seals and omentation oils, and prolonged exposure to fuel causes swelling, cracking and loss of rubber elasticity, causing oil to leak out and oil to enter combustion chambers, creating a vicious cycle of problems.
When replacing the oil after such a malfunction, be sure to rinse the engine with a special washing oil or use cheap mineral oil for short-term work to remove the residue of gasoline.
Ultimately, ignoring the problem leads to liners being turned, cylinder bullies and the need for major engine repairs, which can cost up to 70% of the cost of a new power unit.
Remediation and prevention
The solution begins with changing the oil and the oil filter, but simply changing the liquid is not enough, you need to find and fix the cause, if the problem is in candles or coils, they should be replaced, if a nozzle overflow is suspected, they need to be diagnosed on the stand and ultrasound cleaning.
In case of wear of the piston group, it may be necessary to decoct the rings (unless the wear is critical) or overhaul the engine with the replacement of the piston group. For engines with a mechanical gas pump, it is mandatory to replace the diaphragm or the entire pump assembly.
Preventive measures include:
- 🛢️ Regular oil change according to the regulations, and in severe conditions of operation - more often.
- 🔥 Engine heating before the start of the movement, especially in winter.
- ⛽ Use of quality fuels at the gas stations checked.
☑️ Action plan for the detection of gasoline in oil
These simple rules will help to extend the life of the engine and avoid costly repairs, and remember that oil is the blood of the engine, and its purity directly affects the life of the entire car.
Timely oil change and diagnostics of the ignition system prevent 90% of cases of gasoline entering the crankcase of the engine.
Frequently Asked Questions (FAQ)
Can I get to the service if there is gasoline in the oil?
If the oil level is significantly higher than normal and the smell of gasoline is felt, further operation of the engine may lead to the twisting of the liners, it is better to call a tow truck or replace the oil on the spot if possible.
How long does it take to get the gasoline out of the oil?
Not much. Gasoline doesn't weather itself sufficiently in normal use. On the contrary, it accumulates. It requires a mandatory change of oil and filter after the cause has been eliminated.
Does driving style affect the oil in the oil?
Yes, frequent short-distance trips without full engine heating contribute to fuel condensation and flow into the crankcase; long trips along the highway, on the contrary, help to evaporate moisture and light fuel fractions from the oil (if there are few).
Is diesel in oil as dangerous as gasoline?
Yes, diesel also dilutes oil, although it has a lesser effect on flashpoint, but diesel soot pollutes oil more quickly, and combined with fuel, it causes critical engine wear.