Does switching from 5w30 to 5w40 affect the engine?
2 Answers
Switching from 5w30 to 5w40 does not affect the engine. Engine oil, also known as engine lubricant, serves multiple functions such as lubrication and wear reduction, auxiliary cooling, sealing and leak prevention, rust and corrosion protection, as well as shock absorption. It is often referred to as the "blood" of a car. Below are the key functions of engine oil: Friction reduction: A sufficiently thick oil film separates the surfaces of moving parts, thereby minimizing wear. Sealing: Engine oil forms a seal between the piston rings and pistons, reducing gas leakage and preventing contaminants from entering. Rust prevention: Lubricant adheres to part surfaces, protecting them from water, air, acidic substances, and harmful gases. Shock absorption: When pressure in the engine cylinder rises sharply, suddenly increasing the load on pistons, piston rings, connecting rods, and crankshaft bearings, the lubricant transmitted through the bearings helps cushion the impact. Cleaning: High-quality engine oil carries away carbon deposits, sludge, and metal wear particles from engine components back to the oil pan, flushing away contaminants generated on the working surfaces through oil circulation.
After switching from 5W30 to 5W40 oil last time, I clearly noticed a slight increase in fuel consumption—about 0.5 liters more per 100 kilometers. However, during summer long-distance drives, the engine ran more steadily with reduced noise and was less prone to overheating under high temperatures. The problem arises in winter: cold starts become sluggish, requiring more effort from the battery, and prolonged use may accelerate internal engine wear. In truth, changing oil viscosity isn’t particularly risky—it depends on driving conditions. For hot regions like Hainan, 5W40 offers better protection; in colder northern climates, 5W30 ensures smoother starts. Always remember to check the dipstick regularly and avoid unnecessary viscosity changes.
