You think deep down you both knew the smarter option was to wait for Mr and Mrs Weasley to come back, but I mean... it's just so cool! How often do you get to FLY a car to Hogwarts, plus you needed a way to get there before you miss the feast right?
After a small hiccup of forgetting to turn on the invisibility switch (though you're sure nobody saw you, right?) and a slight dread of not actually finding the train to follow, you finally spot it! The next couple of hours were possibly the most thrilling, bizarre and fun hours of your life! You let Hedwig fly nearby so she could have some fun too and spoke lovely nonsense with Ron.
When you approach the castle grounds, something odd starts to happen to the car. Neither of you are an expert when it comes to cars but the puffing and huffing sounds that are coming from the front sure do not seem right, plus... well, there's smoke???
You look at Ron with sheer panic, who mirrors your face back at you. The car starts falling at a sharper angle than you'd like, whilst Ron frantically tries to reinforce the flying charm (not sure he actually was trying to say any spell, he's was just whacking his wand at the wheel in utter panic murmuring nothing in particular).