If the vehicle manual recommends 5W-20 engine oil but you switch to 5W-30, note that although the two have similar low-temperature starting performance (both 5W grades are suitable for -30°C environments), their high-temperature viscosity differs significantly. The kinematic viscosity of 5W-30 at 100°C (9.3-12.5 mm²/s) is higher than that of 5W-20 (approximately 5.6-9.3 mm²/s). Long-term use may lead to a fuel consumption increase of about 2%-3% due to the higher viscosity, especially for Japanese or hybrid models, whose precisely designed engine clearances are better suited to low-viscosity oil to optimize fuel efficiency. Additionally, if the vehicle is equipped with a particulate filter (such as China 6 emission standard models), the ash content of non-specified viscosity oil may not meet requirements, potentially causing emission system blockage. It should be specifically noted that German models or high-mileage older vehicles may tolerate high-viscosity oil better due to design differences or component wear, but unauthorized specification changes may still void warranty coverage.
