Fluids and filters guide

Fluids and filters have different jobs and intervals

Do not treat “fluids and filters” as one annual bundle. Engine oil, coolant, brake fluid, screenwash, transmission fluid and the various filters have different specifications and replacement/check intervals. Follow the manufacturer information for the exact vehicle.

Engine oil and oil filter

For combustion engines, use the specified oil grade and approvals. Level checks do not replace scheduled oil changes. Overfilling can also cause problems, so follow the handbook method and check on suitable level ground when instructed.

Coolant and brake fluid

Coolant protects against freezing, overheating and corrosion, and incompatible types should not be mixed casually. Brake fluid is safety-critical and absorbs moisture over time; replacement intervals and specifications vary. A falling brake-fluid level can also indicate wear or a fault and should not simply be topped up repeatedly without understanding why.

Air, cabin and fuel filters

The engine air filter protects the intake, cabin filters clean ventilation air, and some vehicles have scheduled fuel-filter replacement. Access and intervals vary. EVs do not have the same engine-related filters but still have cabin filtration and vehicle-specific service items.

Screenwash is simple but important

Maintain sufficient screenwash using a suitable product and concentration. Water alone can freeze and does not provide the same cleaning or protection. Effective washers and wipers matter for visibility and MOT inspection.

What to do next

Use this guide to prepare and ask better questions, not as a remote diagnosis. If a safety-critical defect is suspected, avoid unnecessary driving and arrange a competent physical inspection.