Can 0w and 5w engine oil of the same brand be mixed?

[AdrianFitz]

According to standards, engine oils of different brands and specifications should not be mixed. However, in emergency situations where only a small amount is needed, mixing oils of the same brand is generally not a big issue. Mixing engine oils of the same brand: When topping up engine oil, it is best to use oil of the same brand and specification. If oils are of the same brand but different specifications, they can be mixed, but long-term use is not recommended. Hazards of mixing engine oils of the same brand: Engine oil is primarily composed of base oils and additives, and oils of different specifications are certainly not identical. If two oils of different specifications are mixed, although the lubricating properties remain unchanged, the composition of the oil will inevitably alter. This change in oil composition may adversely affect the engine, hence long-term use of mixed oils of the same brand but different specifications is not advised.

[Hudson]

I once mistakenly mixed a bit of 0W and 5W oil from the same brand, thinking they should be compatible. As a result, the engine noise increased, fuel consumption rose, and inspection revealed unstable mixed viscosity with reduced lubrication effectiveness, nearly damaging components. This lesson taught me that oil viscosities are designed differently—even additives within the same brand may conflict. Mixing without proper ratios can easily cause issues. My advice: always use a single grade during oil changes to avoid makeshift solutions, ensuring engine longevity and peace of mind. Regular maintenance and checking oil quality are crucial—don’t repeat my detour.

[DelAnna]

Oil viscosity ratings like 0W and 5W affect cold-flow performance and protection capability. Mixing them may cause uneven viscosity, insufficient oil film thickness, leading to wear or overheating. There's high risk of additive formulation conflicts that weaken cleaning and anti-wear effects. I emphasize using pure oil of specified grade exclusively. Accidental minor mixing may be tolerable, but large-scale blending risks performance degradation with multiple hazards. For routine maintenance, always select oil as per manual to ensure proper lubrication system operation and prolong engine health.

[ElizaRose]

Mixing 0W and 5W oils of the same brand is unsafe as it interferes with viscosity stability, leading to insufficient engine lubrication and increased risk of failure. I prioritize long-term protection—incorrect viscosity can accelerate component wear, resulting in costly repairs. I trust pure oil formulations for driving safety and reliability, avoiding mixtures. Always inspect carefully during oil changes—don't skip this step.

[MacTanner]

From an economic perspective, mixing engine oils may seem cost-saving in the short term, but it can lead to reduced engine efficiency and higher fuel consumption, ultimately resulting in repair costs far exceeding the price of new oil. I insist on buying full bottles of the same viscosity oil, as the risks of mixing are too great and not worth the gamble. Ensuring stable performance saves money in the long run and protects the engine. Using the recommended type guarantees both economy and practicality.