Bottle of engine oil
A litre of oil can be enough to top up if you get dangerously low and the oil warning light goes on. Running out of oil will cause the engine to seize up. You can also use the engine oil to help lubricate seized nuts and screws and can make the difference between undoing something and fixing it or being stuck at the side of the road.
Screwdrivers
A cross head and flat screwdriver that will fit into most of the screws in the car. When choosing a screwdriver make sure it is good quality - the last thing you want is for the screwdrivers end to burr off the screw or worse just break on you.
A Swiss Army knife
A Swiss Army knife is also a helpful addition to a tool kit especially if it has a saw and few good sharp blades.
Socket set
Each car probably only has 2 or 3 main bolt sizes so make sure that you have the correct sizes with you, carrying smaller and larger socket sizes is just a waste of space and adds to the cars weight.
Rubber bands
These are great for bonding all manner of repairs and can be used to give grip on components which may be covered with oil.
Small Torch
Yes you nearly always break down at night and often in the rain. A small torch will enable you to see better and can highlight leaks of water, oil and exhaust gases easily.
A mobile phone
If all else fails ring for help!
Metallic tape
This is great for fixing exhausts and a double wrap over a hole can enable you to limp home without filling the car with dangerous exhaust fumes. Metallic tape is also good for sealing leaking water hoses and air hoses - again use a double wrap around the area. Gaffer, or elephant tape are also good to carry with you at all times but will not stand up to much heat especially if applied to the exhaust making metallic tape the object of choice. The strengths of gaffer tape lie in its ability to bond to wet surfaces making it ideal for fixing water related leaks.
Clear Plastic Sheet
This can repair a broken window with the use of the tape you carry and can provide a dry surface to work on if the ground is wet.
Length of household electrical wire
You can use this to repair a broken alternator belt, or tie on a loose component or body panel. Also if you have electrical problems you can sometimes use the wire to carry the voltage needed to or from the battery. Run the engine and just touch the wire lightly to see if it is getting warm - if it is exercise extreme caution as an engine fire is the last thing you need.
Jack and wheel brace
Most cars have these and if you get a flat tyre which is probably one of the most common causes of roadside problems you will be thankful that you have these along. The jack can also be used if you need to push out a dented panel following a minor accident or you can use it to pull or push something that is stiff.
Piece of rope
A good sturdy piece of rope which can double up as a tow rope when doubled up or can replace a broken alternator belt.
