The difference between single-grade vs multi-grade oil
Do you know about motor oil grades? For example, what do common grades such as SAE 30, SAE 40, and SAE 5W mean? Why do some motor oil containers say 5W30 or 5W40, and what the single-grade vs multi-grade oil differences between them? Let's take a closer look today.
Let's first look at a set of data.
FeatureSingle-grade OilMulti-grade OilTemperature AdaptabilityNarrow (effective only in a single range)Wide (covers cross-seasonal/regional ranges)Cold Start ProtectionPoor (high viscosity limits fluidity at low temps)Excellent (low-temperature fluidity ensures quick lubrication)High-Temperature Oil Film StrengthAverage (prone to thinning at high temps)Excellent (stable viscosity maintains strong oil films)Usage ConvenienceRequires seasonal oil changesYear-round use; no frequent changes neededCostLower (no complex additives required)Higher (requires viscosity index improvers)
Data shows that single-grade motor oil is only suitable for a single season or fixed temperature environment:
Summer single-grade motor oil (such as SAE 40): Can only be used in high-temperature regions (such as tropical areas) during summer. At low temperatures, it may become too viscous, leading to difficulty in starting the engine.
Winter single-grade motor oil (such as SAE 0W): Can only be used in extremely cold regions during winter. At high temperatures, it may become too thin, causing the oil film to break down.
Multi-grade oil, on the other hand, can cover a wide temperature range across seasons and regions:
5W-30 oil can theoretically be used in environments ranging from -30°C to +40°C (specific ranges should refer to manufacturer standards), eliminating the need to change oil due to seasonal changes. It is widely applicable in regions with distinct seasons or significant temperature fluctuations.
So how do we choose the right motor oil for us?
First, consult your vehicle manual. Each vehicle's engine design, materials, and operating conditions vary, and manufacturers will clearly specify the recommended engine oil viscosity grade (e.g., SAE 5W-30, SAE 10W-40, etc.) and quality grade (e.g., API SP, ACEA A5/B5, etc.) in the User Manual. This is the core basis for selecting engine oil and must be strictly adhered to.
If the manual specifies “SAE 5W-30 (multigrade) motor oil recommended,” then you should choose a multigrade motor oil that meets this viscosity requirement. If it specifies “SAE 40 (monograde) motor oil acceptable,” then monograde oil can be used as an alternative (but modern new cars rarely recommend monograde oil).
The second factor is the engine type.
If permitted by the manual, single-grade oil (SAE 30, 40) can be used as an economical option, but please note:
In cold regions (winter), single-grade oil may cause difficult starting due to viscosity.
Long-term use may accelerate wear due to thinning at high temperatures (decreased oil film strength).
However, modern engines must use multi-grade oil because turbocharged engines operate at higher temperatures (up to 900°C at the turbine end) and direct injection engines are prone to low-speed pre-ignition (LSPI). Both require the high-temperature shear stability (to maintain the oil film) and low ash formulation (to reduce carbon deposits) of multi-grade oil.
Finally, for cars manufactured after 2010, it is recommended to use multi-grade motor oil, and pay attention to the motor oil requirements recommended in the manual.
Tip: If your car has exceeded 100,000 kilometers, I recommend increasing the motor oil viscosity, such as trying 5W40 motor oil, which will make your engine last longer.
