It is necessary to purchase and carry with you on long trips a supply of motor oil and other working fluids, topping them up as needed.
Taking into account the modern design of the car and technology, taking some spare parts with you seems useless, since it is impossible to take everything, and most likely what will break down is what you do not have with you. However, it is still worth paying attention to the most necessary consumables, such as light bulbs for lighting devices, fuses, clamps of various diameters, windshield wipers, spark plugs, a set of two wires in case the engine is started from external power sources (see "Starting the engine from additional power sources"), towing rope (see "Towing a car"), cold welding, insulating tape (with its help you can eliminate not only faulty wires, but also leaking hoses) and other spare parts at your discretion depending on the condition of the car.
Before leaving, be sure to check the tire pressure and tread condition (see "Checking tire pressure" and see. "Wheels, tires and hubs - technical condition check"), as well as lighting fixtures (see "Outdoor lighting and light signaling devices - technical condition check") and the battery to avoid short circuits and failure of electrical consumers (see "Battery - Maintenance").
Be sure to check the condition of the spare tire and bring the air pressure in it to normal. If the spare tire is damaged, replace it. Usually people only remember about the spare tire when they have a punctured tire or damaged a wheel. Such forgetfulness on a long trip can play a cruel joke. Make sure that the tire pump or compressor, as well as the jack and wheel wrench, are in good working order. It would be a good idea to check for the presence of an emergency stop sign in the trunk.
Check the contents of the car first aid kit against the list included with it, paying attention to the expiration dates of the medicines and drugs. It would be a good idea to supplement it with medications from your home medicine cabinet at your own discretion or on the advice of your doctor. Replace expired medications and those whose shelf life is approaching.
And finally, when setting off on a long journey, do not overload the car to the limit (do not exceed the permitted maximum weight specified in the vehicle specifications). Overloading leads to increased wear of tires and suspension parts and loss of directional stability. If, despite the measures taken, a breakdown still occurs, it is better to have with you the phone numbers of any roadside assistance services and some cash.