Q: As I drive away there is a trail of petrol/oil left behind

Hello and thank you for contacting YourMechanic. If you can see a fuel trail behind your vehicle, yes it can be dangerous to drive the vehicle, depending on where the fuel is leaking from. Check under the vehicle to see where the fuel leak is coming from. Look for any connections that are loose and check for any cracks in the fuel lines and the fuel tank. If the fuel is only leaking when the fuel tank is full, then check the fuel neck for leaking fuel. Also, if the fuel is coming out of the top of the fuel tank, either the fuel neck is leaking or the vent valve on the fuel tank is damaged. I recommend not driving the vehicle until the fuel leak is fixed for your safety. If you need further assistance troubleshooting your vehicle, then seek out a technician, such as one from YourMechanic.