Viscosity: The viscosities of these two engine oils are very close, with only a slight difference. 10W30 has a slightly lower viscosity than 10W40. Mixing these oils will result in an oil with a viscosity somewhere between 10W30 and 10W40.
Performance: Engine oils are carefully formulated to meet specific requirements and performance standards. Mixing different oils can alter their properties and may not provide optimal performance. If you have a preference for one type of oil based on your driving conditions, it is better to stick to that oil rather than mixing it with another.
Additives: Engine oils contain various additives that enhance their performance and protect your engine. Different oil brands and formulations may have different additives. Mixing oils can introduce a mixture of additives that may not be compatible with each other, potentially reducing the effectiveness of the oil.
Engine Impact: Mixing different engine oils is unlikely to cause immediate harm to your engine, but it can affect its long-term performance. For example, mixing low-quality or incompatible oils may not provide adequate lubrication, leading to premature wear and tear of engine components.
Compatibility: Some engine manufacturers have specific requirements regarding the type of oil to be used. If your owner's manual specifies a particular oil, it is best to follow it. Mixing oils without checking for compatibility could void your vehicle warranty.
In summary, while mixing 10W40 and 10W30 engine oils is technically possible, it is generally not recommended unless necessary in emergency situations. It's always best to use the oil specified by the manufacturer for your vehicle to ensure optimal performance and protection of your engine.
