For fully synthetic oil, what is the recommended oil-change interval in kilometers?

Answer: B — 10,000 km

Fully synthetic oil lasts longer between changes because it resists oxidation and withstands higher temperatures better than conventional oil. That stability lets engines stay well-lubricated and protected for a longer period, so the oil-change interval can be extended. For most modern engines using fully synthetic oil, the recommended interval is around 10,000 kilometers. Shorter intervals like 5,000 or 7,500 kilometers are more common with conventional oil or under severe driving conditions (lots of short trips, heavy loads, extreme heat). Some vehicles or oils marketed as long-life can go farther, but always follow the vehicle’s manual for the exact interval.