The most important fluid in any modern electric car is the battery coolant. Lithium ion batteries only work efficiently in a certain temperature range, so manufacturers use special coolants (usually ethylene glycol blends) to keep cells cool during rapid charging and in hot weather. If the coolant level drops or the fluid goes bad, you risk overheating, faster battery wear, and in rare cases, even fire. Experts say you should check the battery coolant at least once a year and fully replace it every five to seven years, depending on your car’s service schedule. Never use regular tap water or any fluid that does not have electrical insulation properties.

Another key fluid is brake fluid. Many people think regenerative braking means you never need to worry about the hydraulic system, but that is not true. Regular brake fluid is still your main line of defense for emergency stops. Over time, brake fluid absorbs moisture from the air, which lowers its boiling point and can cause pedal fade or corrosion inside the system. EVs actually need regular fluid checks, especially since their mechanical brakes see less use and problems might go unnoticed until you need them most. Plan to check brake fluid every year, and replace it if you spot discoloration or water buildup.

It might surprise some drivers, but most electric cars still use gearbox oil to keep their single or two speed transmissions running smoothly. Even though there is no multi gear setup like in traditional cars, the reduction gears face extreme forces thanks to instant torque from the motors. This oil protects moving parts and, in some cars, even helps cool the electric motor itself. Although this fluid can last a long time, metal shavings or strange residue in the oil can signal an early mechanical issue. That is why it is smart to have it checked every 100,000 kilometers or as recommended by your automaker.

Finally, do not ignore the windshield washer fluid. It seems minor, but on 2026 electric cars, camera and sensor systems for features like autonomous driving and automatic braking all depend on a clean windshield. Running out of washer fluid, or using poor quality water, can leave streaks or residue that blocks the sensors. This can cause key safety systems to malfunction. If you live somewhere cold, always use a washer fluid that is designed to prevent freezing, so you do not end up with cracked tanks or lines in winter.