The oil system provides filtered oil to all of the following systems, EXCEPT:

The oil system in the T-6 aircraft is designed to supply filtered oil to crucial components that require lubrication and cooling to function effectively. This includes the propeller, reduction gears, and engine, which all rely on oil to maintain operational efficiency and prevent wear.

Specifically, the propeller requires oil for its constant-speed mechanism, ensuring that it can adjust blade pitch appropriately during different phases of flight. The reduction gears also need lubrication to function smoothly, as they transfer power from the engine to the propeller while reducing the rpm. The engine's oil system is vital for cooling and lubricating its internal components, thus maintaining optimal performance.

In contrast, wheel brakes operate independently from the oil system. They rely on a hydraulic system, utilizing brake fluid rather than oil, to create the necessary friction for slowing down or stopping the aircraft. Therefore, the oil system does not provide filtered oil to the wheel brakes, making this answer correct. Understanding the role of different systems in the T-6 aircraft is essential for recognizing how lubrication and hydraulic systems function distinctively within the overall architecture.