For safety reasons, in which order should fuels be checked?

The correct sequence prioritizes safety by considering the density and risk associated with different types of fuels. Diesel is checked first because it has a higher flash point and is less volatile than gasoline, making it less hazardous in terms of fire risk. Following diesel, regular gas is checked next, as it is more volatile and poses a higher risk than diesel. Mid-range fuel, which is a blend between regular and premium, is examined afterward, leading finally to premium gasoline. Premium gasoline is often more sensitive in handling due to its higher volatility. Thus, checking fuels in the order from diesel to premium minimizes the risks associated with flammable liquids, ensuring a safer protocol for handling these materials.