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7 Essential Car Fluids and How to Check Them

What are the 7 essential fluids for car care?

The seven essential car-care fluids are engine oil, coolant, transmission fluid, brake fluid, power steering fluid, windshield washer fluid, and differential fluid. Each has a distinct job, from reducing friction to helping you see clearly. Not every vehicle uses all seven: electric power steering needs no steering fluid, and some drivetrains do not have a separate differential-fluid reservoir.

Our team recommends using your owner’s manual to identify the correct fluid specifications, inspection procedures, and service intervals for your vehicle. For more detail, see our guide to checking and refilling essential car fluids.

1. Engine oil

Engine oil lubricates moving parts and helps carry away heat. Check the level with the dipstick or electronic oil monitor, following your manual’s instructions. Add oil of the specified viscosity and service rating if the level is low, and avoid overfilling.

2. Coolant

Coolant helps regulate engine temperature and protects against freezing and corrosion. Inspect the level at the marked reservoir when the engine is cold. Use the coolant type and water mixture specified for your vehicle; never open a hot pressurized cooling system.

3. Transmission fluid

Transmission fluid lubricates internal components and supports operation. Some vehicles have a dipstick, while others require a specific temperature and service procedure. Use only the specified fluid, since automatic, manual, and continuously variable transmissions can have different requirements.

4. Brake fluid

Brake fluid transfers force through the braking system. Check the level through the translucent reservoir and use the specified DOT rating if topping off is appropriate. A falling level can indicate worn brake pads or a leak, so have the brakes inspected rather than repeatedly adding fluid.

5. Power steering fluid

Hydraulic power steering systems use fluid to make steering easier. Check the reservoir markings and use the specified fluid; some systems require automatic transmission fluid instead of conventional power steering fluid. Vehicles with electric power steering do not need it.

6. Windshield washer fluid

Washer fluid removes road grime from your windshield. Refill the marked reservoir with a ready-to-use formula suited to your climate, including freeze protection when needed. Do not substitute coolant or plain water.

7. Differential fluid

Differential fluid lubricates gears that allow driven wheels to turn at different speeds. Its fill plugs are usually underneath the vehicle, so our team recommends professional service if you cannot safely access them. Use the specified gear oil and any required additives.