Checking the oil level in the engine is necessary on a daily basis for routine maintenance of a tractor. This is because the engine oil plays a crucial role in lubricating and cooling the engine components, which helps to prevent wear and tear and prolong the engine's lifespan. By checking the oil level daily, you can ensure that the engine is properly lubricated and prevent damage due to low oil levels.
On the other hand, draining the gear box oil, removing and cleaning the engine's air filter, and replacing the fuel filter element are also important maintenance tasks, but they do not need to be done on a daily basis. Draining the gear box oil, for example, may be done as part of regular maintenance, such as every 50 or 100 hours of operation. Cleaning the air filter and replacing the fuel filter element may be done based on the manufacturer's recommendations, which could be every 100 or 200 hours of operation, or at a certain time interval.
In summary, checking the oil level in the engine is a daily routine maintenance task for a tractor, while other maintenance tasks such as draining the gear box oil, cleaning the air filter, and replacing the fuel filter element are done less frequently based on the manufacturer's recommendations.