There’s a large debate about the type of petrol the vast majority of unleaded cars should run on. Many mechanics will tell you that 95 octane should be your go-to, particularly if you’re running an older car. For most newer cars, 91 (or E10) is generally the choice for most people. This is fine, but be aware that it has hydroscopic qualities, meaning it has a greater potential of introducing water and contaminants in the engine. It’s always good to run a higher octane fuel, as they generally help keep your engine cleaner and more efficient.