Once youve packed the boot, strapped the kids into the back, checked the tyre pressures and selected the right CDs for the journey, you probably think youre well prepared for a long trip.
The chances are, though, youve given little thought to fuel. No, not the cars - yours.
If your idea of in-car eating is a few packets of wine gums and a pork pie after junction 16, think again.
Fill up before you set off
When you want to avoid the rush hour or youve an early flight to catch, skipping breakfast seems like a great time-saver.
Miss your cornflakes, though, and youre setting yourself up for a miserable journey.
'You should always avoid driving on an empty stomach,' says Claire Williamson, a nutrition scientist at the British Nutrition Foundation.
'Driving when youre hungry can have a negative effect on your mood and concentration.
'Youre also more likely to become irritable, which is never a good thing behind the wheel.'
Sadly, a fry-up isnt the best pre-drive breakfast - instead, keep it simple and carbohydrate-heavy.
Carbohydrates will provide the energy you need to help you concentrate on the road and prevent you from falling asleep at the wheel.
Not all carbs are the same, though - they deliver their energy at different rates, measured by something called the Glycaemic Index.
Foods with a high GI such as bagels, white bread and fizzy drinks deliver energy rapidly, but once that initial rush subsides youll soon feel hungry.
Drivers should opt for foods with a moderate or low GI, as they provide a steady and sustained flow of fuel.
At breakfast, bowls of low-GI muesli, porridge or bran flakes are a great choice, or you could opt for moderate-GI baked beans on higher-GI toast.
Resist the temptation of an extra doughnut at the service area, because stuffing yourself wont add to your motoring pleasure.
'Avoid big meals, especially ones that are greasy or high in protein,' says Williamson.
'Over-indulge, and the food will sit in your stomach, and youll feel bloated once you set off.
'Theres also the chance that youll suffer from indigestion, and a big meal can make you feel sleepy.'
Instead, eat three to four light meals at regular intervals throughout the day.
You could even take a leaf out of the book of marathon runners and Tour de France cyclists, and snack on energy-boosting sports bars.