Should Older Cars Use 10w40 or 5w40?

[MacDawson]

Both 10w40 and 5w40 engine oils can be used for older cars, with the choice primarily depending on the local environmental conditions. Method for Changing Engine Oil: Use a jack to lift the vehicle, locate and loosen the oil drain bolt to drain the oil; after removing the oil filter, place a container beneath it; replace with a new oil filter and add new engine oil. Functions of Engine Oil: Reduces friction and high temperatures; cools and lowers temperature; cleans and purifies; absorbs shocks and cushions; prevents rust and corrosion. Engine oil, also known as motor lubricant, is composed of base oil and additives. The base oil is the main component of the lubricant, determining its fundamental properties, while the additives compensate for and improve any deficiencies in the base oil's performance. Meaning of Engine Oil Grades: The "w" stands for winter, and the smaller the number before it, the better the oil's low-temperature fluidity, indicating a lower usable environmental temperature and better engine protection during cold starts. The number after "w" indicates the oil's high-temperature resistance, with higher numbers representing better protective performance under high temperatures. Classification of Engine Oils: Conventional mineral oil, semi-synthetic oil, and full synthetic oil. Mineral oil is a commonly used lubricant on the market, derived from useful substances during the petroleum refining process. Semi-synthetic oil uses semi-synthetic base oil, a product purified from mineral oil through hydrocracking technology. Full synthetic oil is the highest grade of engine oil.

[FernandoAnn]

This old buddy of mine has been with me for almost 15 years, so choosing engine oil requires real attention. Older car engines have larger wear gaps between parts, and the higher viscosity of 10w40 forms a thicker oil film to protect components, while also maintaining stable oil pressure at high speeds. 5w40 offers better low-temperature fluidity, making cold starts smoother in winter temperatures as low as -20°C, but its high-temperature protection isn’t as good as 10w40. I noticed that when running the AC and climbing hills in summer, 5w40 burned off faster, so I’ve stuck with 10w40 ever since. It really depends on where you drive—those in extremely cold northern regions might consider 5w40, but 10w40 is perfectly sufficient in the south and costs a third less. Every oil change, I keep an eye on the dipstick—frequent maintenance is key for older cars.

[LiamAnn]

We veteran car owners dread oil burning the most, so choosing the right viscosity is crucial. 10w40 has higher viscosity than 5w40, making it particularly suitable for older vehicles with over 100,000 kilometers, as it better fills the gaps caused by piston ring wear and reduces blue smoke. Last time I tried 5w40 on a long trip, the engine sounded loose once the oil warmed up, but switching back to 10w40 immediately made it much quieter. However, if you frequently drive in Northeast China, you should opt for 5w40 in winter for easier cold starts. I usually stock two types of oil: 10w40 for summer and switch to 5w40 before winter. Also, remember to change the oil filter frequently—older cars can't handle impurities well.

[Malia]

Choosing engine oil for old cars is straightforward: consider the wear level and usage environment. New engines have tighter clearances, making 5w40 better for low-temperature protection. However, as parts wear and clearances increase in older cars, 10w40's higher high-temperature viscosity adheres better to component surfaces. With over 20 years in auto repair, I've seen countless cases of cylinder scoring due to wrong oil choices in old cars. If you notice a burnt smell from the exhaust or significantly increased oil consumption, immediate inspection is crucial. For vehicles over 100,000 km, prioritize 10w40 unless you're in extreme cold like Harbin. Regular oil pan checks are also essential.

[OSophia]

My old Santana has clocked 300,000 kilometers, and I've tried various engine oils. When choosing oil for an old car, don't just look at the specifications—actual performance matters: using 10w40 reduced engine idle vibration and improved climbing stability, while 5w40 offered quicker cold starts but lower high-speed oil pressure. First, check the maintenance manual to confirm the original viscosity standard; most older German cars originally recommended 5w40. If you notice blue smoke from the exhaust or rapid oil consumption, it indicates a need for higher viscosity 10w40. Remember to replace the sealing gaskets during oil changes—leaks in older cars often stem from these small components.

[EmmanuelDella]

Engine wear is a critical factor in selecting motor oil. For new cars with component clearances around 0.02mm, 5W40 is ideal. However, after 200,000 kilometers when clearances exceed 0.1mm, switching to 10W40 becomes necessary to compensate. During my last engine teardown, I personally observed the wear gap in piston rings, which truly clarified the significance of oil viscosity. While 5W40 offers slightly better cold-start protection, 10W40 provides superior oil film strength at high-temperature operations of 90°C. I make it a practice to check my oil condition every 5,000 kilometers - if it appears darkened or thinned, it's time for a change. For older vehicles, it's crucial to avoid mixing different oil brands as conflicting base oil formulations can actually cause engine damage.