What is the difference between 5w30 and 5w20?
2 Answers
5w30 and 5w20 have the following differences: 1. Different oil viscosity: mainly the high-temperature viscosity of the oil. 5w20 has lower viscosity (between 5.6-9.3), which is relatively fuel-efficient and makes the vehicle feel lighter during driving, while 5W-30 has higher viscosity (between 9.3-12.5), which is relatively more fuel-consuming and makes the throttle feel heavier, but the engine noise is smaller. 2. Different sealing performance: the higher the viscosity, the better the sealing performance. The number after W in 5w30 and 5w20 represents the high-temperature viscosity, so 5w30 oil has better sealing performance than 5w20 oil. However, higher viscosity is not always better because the higher the viscosity, the greater the friction, and the greater the engine power loss.
I've been in the auto repair industry for over a decade and have personally changed countless engine oils. The core difference between 5W30 and 5W20 lies in their high-temperature performance: the '20' after the W in 5W20 indicates it's thinner and flows faster, saving fuel but potentially offering insufficient protection at high RPMs or in hot weather; 5W30's '30' means it's slightly more viscous, thicker when the engine is hot, and better at handling load, making it suitable for older cars or tropical regions. Both start with W5 for cold starts, so there's no difference in winter sub-zero conditions. The problem is, in my repair work, I've seen many car owners blindly switch oils—20 oil saves 2-3% on fuel, but accelerates engine wear; the manual is the gold standard, and using lower viscosity oil improperly may lead to premature repairs. Based on experience, city cars can use 20 without issues, while off-road or high-displacement vehicles are better off with 30—don't save small money only to lose big money.
