Should older cars use 5w30 or 5w40?

[LylaLynn]

Here are the methods to determine which type of engine oil to use for older cars: 1. Generally, due to engine craftsmanship and cylinder wear, older cars require engine oil to participate in sealing, so it is recommended to use 5w40 oil. 2. The specific model of the car should be considered, along with the environmental temperature of the region where the vehicle is used and the recommended oil type in the vehicle's maintenance manual. Here is some information about engine oil: 1. There are many types of engine oil with different specifications, each representing different performance characteristics. 2. The main difference between 5w30 and 5w40 is that 5W-30 has relatively better fluidity, which can more effectively reduce fuel consumption and allow the engine to dissipate heat faster and more efficiently.

[AlexandraDella]

For my 15-year-old ride, 5W40 is the more reliable choice. Older engines develop increased internal clearances, and metal surfaces inevitably wear after high mileage – thicker viscosity oil does a better job filling those gaps. I tried 5W30 before but noticed sluggish throttle response and slightly higher fuel consumption. My mechanic explained the oil was too thin to maintain proper sealing, causing some cylinder pressure leakage. Now running 5W40 during summer with AC on highway drives, the high-temperature protection is noticeably superior, and the oil pressure gauge stays much steadier. One caveat: if you primarily do slow city driving with a well-maintained older vehicle, 5W30 could work, but you'll need to check the dipstick frequently for abnormal oil consumption.

[LukeMarie]

A friend's old car with 200,000 kilometers on it has gone through this choice. He drives in northern regions year-round and has to start the car even at -20°C in winter. The low-temperature fluidity of 5W40 is actually similar to 5W30, ensuring smooth cold starts. The key difference lies in high-temperature protection. During long-distance drives, he noticed significantly reduced oil consumption with 5W40, and the exhaust was less blue. Later, upon engine disassembly, it was clear that the piston ring gaps were indeed quite large, and the higher-viscosity oil film provided better protection for the worn parts. However, the specific choice depends on the car's condition. His car's manual allows for 5W30, but the repair shop recommended 40 for high-mileage use. Now, with a 12,000-kilometer oil change interval, it's working perfectly fine.

[DeIsabelle]

Last year, I faced this dilemma when changing the oil for my dad's old car. The mechanic said three factors matter: mileage, oil consumption, and driving habits. If the car has over 150,000 km and burns oil significantly, you must use 5w40. That was exactly the case with my dad's car—previously using 30-weight oil, it needed half a liter top-up every 2,000 km. Switching to 40 improved things a lot. But be mindful of oil passage clearance; overly thick oil might affect hydraulic lifters. Also, frequent aggressive driving calls for 40-weight oil for better protection. We ultimately chose Shell 5w40 full synthetic, paired with an engine flush to clean sludge—now the engine runs smoother.

[JaydenDella]

Handled many classic car maintenance cases. 5W30 and 40 have similar low-temperature performance, differing mainly in viscosity at 100°C. Older engines with metal fatigue have larger clearances, requiring higher viscosity oil to form thicker protective films. A classic example: a 1998 Accord developed valve noise after switching to 30-weight oil, but quieted down when reverting to 40-weight. However, don't change blindly - first check the factory manual. Some older German cars may specify 40-weight from factory. Japanese cars in good condition can continue using 30-weight. Recommend using 40-weight for vehicles over 100,000km, especially in hot southern regions. After oil change, monitor cold-start noises - excessively thick oil may cause delayed pump priming.

[StAshlyn]

Conducted a comparative test on the performance of two oils in an old car. Using the same Camry with 200,000 kilometers, switching to 5W40 resulted in a 0.3L increase in fuel consumption but halved the oil consumption. The key factor is the high-temperature high-shear (HTHS) value; the 40-grade has a higher HTHS, providing more effective protection for worn bearings. Northern users need not worry about winter starts, as both 5W prefix oils meet the -30°C requirement. A tip: flush the oil passages with a cleaning oil before changing to avoid high-viscosity oil dislodging carbon deposits and causing blockages. My old Audi, after switching to Motul 5W40, now shows no drop in oil level on the dipstick even after 5,000 kilometers, whereas with 30-grade oil, I had to keep spare oil in the trunk.