5w30 motor oil’s ability to function in a large variety of engine types and under a wide range of temperature conditions makes it incredibly versatile. Whether you have a light-duty petrol or diesel engine, 5w30 is often the suggested motor oil to use because it flows more easily in winter temperatures. At the same time, it’s able to maintain a safe viscosity when the engine is hard at work in the summer heat, when an oil with lower viscosity is more likely to break down, thereby causing greater wear on engine parts.