Coolant is pumped around the engine, cooling it via the radiator. Low levels mean the car can overheat and the engine becomes damaged. While you may need to top up every now and again, regular topping up could mean there's a leak that should be investigated. Use the right type of coolant for topping up as some cars use coolant which shouldn't be mixed with other types. Check the level once a week, or before a long journey and replace when the manufacturer recommends.

1. Check the level is at the right mark. If you need to remove the reservoir cap, carefully unscrew the cap and check the level.
2. If the level’s low, top up using 50/50 mixture of water and antifreeze (or clean tap water in an emergency) to the right mark. Don’t overfill.
3. Refit the cap tightly afterwards, and wipe away any spillage.