What are the requirements of lubricating oils for diesel engines?

The selected combination of requirements for lubricating oils in diesel engines is indeed correct. Each of the three points contributes to the overall performance and efficiency of the engine, which is critical for safety and compliance with regulations.

1. Reducing wear: This is essential as it prolongs the life of engine components, ensuring the vehicle operates safely over time. Proper lubrication minimizes friction between moving parts, which is a fundamental requirement according to various German regulations that prioritize vehicle maintenance.

2. Heat resistance: Diesel engines can reach high temperatures during operation. Heat-resistant oils prevent breakdown and maintain performance, which is vital to avoid engine failure while driving.

3. Fluidity during cold periods: Oil must be able to flow easily even in low temperatures to ensure the engine starts properly and operates smoothly, especially in colder climates common in Germany. This characteristic is crucial for maintaining optimal performance under various weather conditions.

Overall, selecting all these options reflects a comprehensive understanding of the necessary properties of lubricating oils, directly tied to both vehicle safety and compliance with German traffic laws, which emphasize regular vehicle maintenance and performance for public safety.