It’s not advisable to put water directly into a car battery unless it’s specifically designed as a maintenance-free battery. Traditional lead-acid car batteries require distilled water to replenish the electrolyte levels. However, adding water to a car battery should only be done if the electrolyte levels are low.

Here are some important points to consider:

1. Safety first: When dealing with car batteries, always wear gloves and eye protection. Battery acid can be harmful if it comes into contact with your skin or eyes.
2. Check the type of battery: Maintenance-free batteries typically don’t require adding water because they are sealed. However, traditional lead-acid batteries may need water periodically.
3. Use distilled water: Never use tap water or any other type of water besides distilled water. Tap water contains minerals and impurities that can harm the battery.
4. Check the electrolyte level: If the electrolyte level in the battery cells is below the recommended level, you can carefully add distilled water to bring it up to the appropriate level. Don’t overfill, as this can cause electrolyte overflow when the battery heats up.
5. Follow manufacturer instructions: Always refer to the manufacturer’s instructions for specific guidance on maintaining your car battery.

If you’re unsure about whether your battery needs water or how to add it safely, it’s best to consult a professional mechanic or refer to your vehicle’s manual for guidance.

Determining the “longest-lasting” car battery can be subjective and dependent on various factors such as driving habits, climate, maintenance, and the specific needs of your vehicle. However, some brands are well-known for producing high-quality and durable car batteries. Here are a few reputable brands:

1. Optima Batteries: Optima batteries are known for their durability and ability to withstand harsh conditions. They use a unique spiral-cell design that provides a longer lifespan and superior performance compared to traditional lead-acid batteries.
2. Odyssey Batteries: Odyssey batteries are designed to deliver high starting power and deep cycling capability, making them suitable for vehicles with high electrical demands or frequent starts. They are known for their long service life and reliability.
3. ACDelco: ACDelco produces a wide range of automotive batteries known for their quality and durability. They offer various types of batteries to suit different vehicles and driving conditions.
4. Exide: Exide is another reputable brand that manufactures reliable car batteries. They offer a range of battery types, including lead-acid and AGM batteries, with a focus on performance and longevity.
5. DieHard: DieHard batteries are known for their reliability and strong starting power. They are designed to withstand extreme temperatures and provide consistent performance over time.

Ultimately, the longevity of a car battery depends on factors such as proper maintenance, usage patterns, and environmental conditions. Regularly checking and maintaining your battery, along with choosing a reputable brand, can help ensure you get the longest possible lifespan out of your car battery.