The core reason why engine oil must be replaced regularly

The core reason why engine oil must be replaced regularly

Engine oil not only lubricates, but also performs five functions: lubrication, cooling, cleaning, sealing, and rust prevention. After long-term use, it will completely lose its effectiveness and not replacing it will directly damage the engine.

1. The oil will continuously oxidize and deteriorate

The engine operates at extremely high temperatures (thousands of degrees in the cylinder, and the oil temperature is always 80-120℃). When exposed to high temperatures and air, the oil will oxidize:

Forming sludge, gums, and varnish, adhering to pistons, valves, and oil passages;

The viscosity of the oil thickens or thins, losing its normal lubrication ability;

Producing acidic substances, corroding the crankshaft, bearings, and metal parts of the cylinder wall.

2. Continuously mixed with impurities, causing severe pollution

During the combustion process of the gasoline engine, pollutants are continuously generated and dissolved in the engine oil:

Combustion carbon deposits, metal debris: fine iron particles fall off from the piston, crankshaft, and gears during friction;

Unburned gasoline: When the engine is cold-started or driven for short distances, the gasoline enters the crankcase and dilutes the engine oil, making it thinner and with insufficient pressure;

Water vapor, acidic exhaust gas: Combustion produces water vapor that condenses and mixes with sulfides to form acid, corroding the components;

The accumulation of impurities will clog the oil filter and small oil passages, causing local lack of oil and dry grinding.

3. Additives are exhausted

New engine oil contains a large amount of functional additives, which are the key to the performance of the oil:

Detergent dispersants: Dissolving sludge and suspending impurities

Anti-wear agents: Protecting crankshafts, cams, and piston rings

Antioxidants, rust inhibitors, viscosity stabilizers

After long-term operation, the additives gradually deplete, leaving only the base oil, and losing its protective ability.

4. The serious consequences of not replacing engine oil on time

Lubrication failure, seizing cylinder, seizing bearing: The oil film breaks, and metal directly rubs against each other. In mild cases, there will be abnormal sounds and power loss; in severe cases, the crankshaft will be seized and the engine will be directly scrapped;

Oil passage blockage: Sludge blocks the oil passages, causing local components to have no oil for cooling and lubrication;

Oil seal aging and leakage: The deteriorated engine oil corrodes the rubber oil seal, resulting in leakage and oil loss;

Fuel consumption increases, power weakens: The piston ring is stuck by carbon deposits, the seal is poor, and the engine burns oil and emits smoke;

Components wear out rapidly: Bearings, camshafts, and timing systems have a significant reduction in lifespan.

Additional note: Special points for small gasoline engines in gardens (mower, chainsaw, GX35 type)

These two-stroke / four-stroke small engines have extremely high rotational speeds, poor heat dissipation, and harsh working conditions. The oil ages much faster than that of cars, and the replacement cycle is shorter:

Four-stroke garden engines: Generally, the oil should be replaced every 20-50 hours

For long-term overloading operation, it is recommended to shorten the replacement cycle

Summary: Engine oil is the "blood" of the engine. High temperatures, impurities, and consumption will continuously damage its protective ability. Replacing engine oil regularly is the lowest-cost and most effective means of protecting the engine.