Filling up with the wrong fuel is not uncommon, but this could make your engine sluggish or even destroy it. Mixing up lead-replacement and unleaded petrol won’t do much damage but pour diesel into a petrol tank – or vice versa – and your whole fuel system will have to be cleaned out. If you notice the error early enough, don’t drive. Cleaning your tank is a fairly simple process but starting your car with the wrong fuel inside could destroy your engine and the cost of repairs could run into tens of thousands.
It might be more convenient to sit in your car while the garage attendant fills her up but it’s important to be sure that your fuel cap is closed properly. Driving without a fuel cap or with an open fuel cap is dangerous. It’s illegal too. Without a closed cap, your car expels fumes and it’s this gas – not the liquid inside – that is most flammable. As the components of your car heat up while you’re driving, it could catch alight. You could also spill fuel onto the road, making it slippery and dangerous for yourself and other drivers.