If you don’t have the owner’s manual, you can also:

1. Check the Oil Dipstick: Some dipsticks have markers indicating the oil level and may also indicate the capacity.
2. Look for a Label under the Hood: Some cars have a label under the hood that indicates the type and amount of oil needed.
3. Visit the Manufacturer’s Website: Often, you can find this information online on the car manufacturer‘s website or through an online car manual database.

If you provide the make, model, and year of your car, I can give you a more precise estimate.

Motor oil serves several critical functions in the operation and longevity of an engine. Here are the main functions:

1. Lubrication: Motor oil reduces friction between the moving parts of the engine, such as pistons, bearings, and camshafts. This reduces wear and tear, extending the life of the engine.
2. Cooling: By reducing friction, motor oil helps to dissipate heat away from the moving parts, assisting the engine’s cooling system in maintaining optimal operating temperatures.
3. Cleaning: Motor oil contains detergents and additives that help clean the engine by preventing the buildup of sludge and varnish, which can impede engine performance.
4. Protection Against Corrosion: Motor oil creates a protective film over engine parts, preventing exposure to moisture and acids that can cause corrosion and rust.
5. Sealing: Motor oil helps seal tiny gaps between the piston rings and cylinder walls, enhancing engine compression and efficiency.
6. Suspension of Contaminants: Motor oil captures and suspends contaminants like dirt, metal particles, and combustion by-products, preventing them from settling and causing damage. These contaminants are then removed when the oil is changed.
7. Enhanced Performance: High-quality motor oil can improve engine performance and fuel efficiency by ensuring that all parts operate smoothly and effectively.

Regular oil changes are essential to maintain these functions and ensure the engine runs smoothly and efficiently.

The frequency of synthetic oil changes can vary depending on several factors, including the make and model of your vehicle, your driving habits, and the type of synthetic oil used. Generally, the recommended interval for changing synthetic oil ranges from 7,500 to 10,000 miles (about 12,000 to 16,000 kilometers) or every six months to a year, whichever comes first.

However, it’s essential to consider the following factors:

1. Manufacturer’s Recommendations: Always refer to your vehicle’s owner’s manual for the manufacturer’s recommended oil change intervals. Some manufacturers may specify longer intervals for synthetic oil.
2. Driving Conditions: If you drive under severe conditions, such as frequent short trips, extreme temperatures, towing, or driving in dusty or dirty environments, you may need to change the oil more frequently.
3. Oil Quality: Higher-quality synthetic oils can last longer and offer better protection, allowing for extended oil change intervals.
4. Monitoring Oil Life: Many modern vehicles have oil life monitoring systems that alert you when it’s time to change the oil based on your driving patterns and engine conditions. Rely on this system if your car is equipped with it.

In summary, while a general guideline is to change synthetic oil every 7,500 to 10,000 miles or every six months to a year, it’s crucial to follow the specific recommendations for your vehicle and consider your driving conditions.