As the UK basks in summer sunshine, millions of drivers are unknowingly risking a colossal fine and penalty points for a simple but critical car maintenance error. The mistake? Topping up their vehicle's coolant system with plain water instead of the proper antifreeze and coolant mixture.
This seemingly innocent shortcut, often taken to save a few pounds during the warmer months, is a direct violation of The Road Vehicles (Construction and Use) Regulations 1986. Motorists caught with an improper coolant mixture could be slapped with a £1,000 fine for driving a vehicle in a dangerous condition. If the issue is severe enough to be deemed a 'dangerous defect', the penalty skyrockets to a maximum of £2,500, a driving ban, and three penalty points.
Why Water Isn't Enough
Coolant, or antifreeze, does far more than just stop water from freezing in winter. It contains essential lubricants and corrosion inhibitors that protect your engine's vital components, including the water pump. Using plain water, especially hard tap water common in many UK regions, can lead to:
- Limescale build-up: Clogging the narrow channels in the radiator and engine block, leading to overheating.
- Corrosion: Eating away at the aluminium, rubber, and plastic parts inside the cooling system, causing premature failure and potentially catastrophic leaks.
- Boiling Over: A weakened coolant mixture has a lower boiling point, increasing the risk of your engine overheating and breaking down during a summer traffic jam or on a long motorway journey.
The MOT and Insurance Implications
The repercussions extend beyond an on-the-spot fine. A car with a clearly weakened or incorrect coolant mixture is likely to fail its MOT.
Perhaps more alarmingly, if an engine failure caused by incorrect coolant leads to an accident, your insurance provider could refuse to pay out. They may argue that the driver failed to maintain the vehicle in a roadworthy condition, invalidating the policy and leaving you personally liable for all costs.
Expert Advice for Summer Driving
Tim Alcock from LeaseCar.uk advises drivers to be vigilant: "It can be tempting to cut corners... but it's a huge mistake that could invalidate your car insurance if the worst happens."
The correct course of action is to always use a pre-mixed coolant or a concentrate diluted with deionised or distilled water in the ratio specified by your vehicle's manufacturer (typically 50/50). This ensures optimal boiling and freezing protection, lubrication, and corrosion prevention year-round.
Before embarking on any long summer trips, take a moment to check your coolant level and condition. It's a simple five-minute check that could save you thousands of pounds and keep you safe on Britain's roads this summer.
