Will switching from 5w30 to 5w40 have any impact?
2 Answers
Switching from 5W30 to 5W40 engine oil has no negative impact. The number 40 indicates that the oil has better high-temperature tolerance compared to 30. One of the key aspects of car maintenance is changing the engine oil. When replacing the oil, car owners should pay attention to the oil's specifications, which are often marked on the packaging as 5W30 or 5W40. Below are the functions of engine oil: Friction reduction: A sufficiently thick oil film separates the surfaces of sliding parts, thereby reducing wear. Sealing: Engine oil forms a seal between the piston rings and pistons, reducing gas leakage and preventing contaminants from entering. Rust prevention: Lubricating oil adheres to part surfaces, protecting them from water, air, acidic substances, and harmful gases. Cushioning: When pressure in the engine cylinder rises sharply, suddenly increasing the load on pistons, piston skirts, connecting rods, and crankshaft bearings, the lubricated transmission through bearings helps cushion the impact load. Cleaning: High-quality engine oil can carry carbon deposits, sludge, and worn metal particles back to the oil tank through circulation, washing away contaminants generated on the working surfaces of parts.
With years of car experience, switching from 5w30 to 5w40 does bring some changes, mainly because the number 40 indicates higher high-temperature viscosity. The increased viscosity provides better lubrication for engine components, protecting them from wear during hot weather or long-distance high-speed driving. For instance, when driving on mountain roads in summer, I noticed the engine runs smoother with less noise. However, the downside is increased engine resistance, which may raise fuel consumption by a few tenths of a liter per 100 km, especially noticeable in city driving. As for cold starts, both oils start with 5w, meaning they share the same low-temperature viscosity, so winter performance differences are minimal. Additionally, engine design plays a crucial role—newer models optimized for low-viscosity oils for fuel efficiency may experience slightly reduced performance or softer acceleration if switched to higher viscosity oils not recommended by the manufacturer. While the impact is minor, it’s advisable to check the vehicle manual before making any changes and stick to regular maintenance, ensuring oil pressure remains normal. Small changes can accumulate, affecting both economy and performance, so the best practice is to follow the manufacturer’s oil recommendations for long-term stability.
