A swollen car battery is a serious warning sign. The case should be flat and firm, not bulging, rounded, or distorted. Once a battery swells, it is usually unsafe to keep using it because internal

If your car interior lights won’t turn off, the battery can drain overnight and leave you with a no-start situation. The cause is usually simple: a dimmer switch left on, a door not fully latched,

A knocking sound under the car when accelerating usually means something is moving, loading, or vibrating more than it should when engine torque is applied. The sound can come from the drivetrain, suspension, exhaust, engine

Adding water to a car battery is only correct for a specific type of battery: a serviceable flooded lead-acid battery with removable caps. If your battery is sealed, maintenance-free, AGM, EFB, or gel, you should

Turning off a car while driving is one of those things many drivers wonder about but should almost never try on purpose. What happens depends on the vehicle, the key or push-button system, your speed,

Putting a modern car in neutral while coasting usually does not save gas. In gear, many fuel-injected engines can cut fuel completely while preserving engine braking.

Leaving a manual car in gear when parked is usually safe when the parking brake is applied first. The gear should act as backup, not the main holding system.

An EGR delete can reduce intake soot, but it can also be illegal for road use and may create emissions, calibration, inspection, and reliability problems.