Modern cars rely on a system of fluids to keep the engine cool, the brakes working, the transmission shifting smoothly, and the power steering responsive. When any of these fluids runs low or degrades, it creates immediate risk — from brake failure to engine overheating. The good news is that checking all six fluids takes about 15 minutes and requires no tools. Here's your complete guide to every fluid in your car.
Engine oil lubricates and cools internal engine components. Check it monthly using the dipstick (see our Oil Level guide). Change it every 3,000–7,500 miles depending on oil type. Use the grade specified in your owner's manual — using the wrong viscosity can reduce engine protection.
Coolant prevents your engine from overheating in summer and freezing in winter. Check it in the translucent plastic overflow reservoir next to the radiator — never open the radiator cap when the engine is hot. The level should sit between MIN and MAX. Coolant should be flushed every 30,000–50,000 miles.
Brake fluid transmits the force from your brake pedal to your brake calipers. Check it in the small plastic reservoir on top of the master cylinder under the hood — it's usually labeled 'BRAKE'. The fluid should be clear to light yellow; if it's dark brown, it's absorbed moisture and needs flushing. Low brake fluid can indicate a leak.
If your car has hydraulic power steering (not electric), it uses power steering fluid. Check the reservoir (usually labeled with a steering wheel icon) with the engine warm. Low fluid causes heavy, difficult steering and grinding noises. Some cars have electric power steering and don't use this fluid at all.
Transmission fluid lubricates gears and keeps your transmission shifting smoothly. Most cars have a transmission dipstick (similar to the oil dipstick but usually further back in the engine bay). Good transmission fluid is bright red and slightly sweet-smelling. Dark brown or burnt-smelling fluid needs changing immediately.
This is the easiest fluid to check and refill — just open the reservoir with the windshield wiper icon and top it up. Never use plain water, as it doesn't clean as well, can freeze in winter, and promotes algae growth in summer. Use a pre-mixed washer fluid rated for your climate.
A fluid level that keeps dropping despite refilling indicates a leak. Oil on your driveway, sweet-smelling steam from the engine, or a burning smell inside the car are all signs of a leak. Some leaks are minor; others are urgent. Either way, a mechanic should inspect it — Carofix can get you connected fast.
The simplest routine: check oil and washer fluid monthly, coolant and power steering fluid every 3 months, and brake and transmission fluid every 6 months. Keep a small notepad in the glove box to log levels and dates — patterns tell you a lot about your car's health over time.
Coolant is pressurized and can be 230°F or hotter. Opening the radiator cap on a hot engine can spray scalding coolant directly at your face. Always wait at least 30–45 minutes after the engine has been running before opening the radiator cap. Check the overflow reservoir instead — it's always safe to open.
If you notice your car is consistently consuming a particular fluid faster than it should, don't just keep topping it up — that's masking a problem. Carofix can connect you with a mechanic to find and fix the source leak, saving you from a much bigger repair down the road.
Fill out one form and Carofix contacts trusted mechanics and service vendors directly on your behalf — no phone calls, no stress.
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