Can I mix two different types of oil?

Lubricants are always optimized to meet the requirements of international classifications (API, ACEA). However, there are many ways of formulating a specific type of lubricant. Mixing two oils that have equivalent properties will not pose a problem, but final performance cannot be guaranteed. All market oils (petrol engine or diesel, mineral or synthetic) are mixable. However, a blending of two oil qualities lower the superior quality.