Final answer:
The likely cause of excessive oil consumption in a reciprocating engine without evidence of leaks is worn piston rings or valve seals. To address this issue, the worn piston rings or valve seals would need to be replaced to restore the proper function of the engine and reduce oil consumption.
Step-by-step explanation:
The likely cause of excessive oil consumption in a reciprocating engine without evidence of leaks is worn piston rings or valve seals. These components help to seal the combustion chamber and prevent oil from entering the combustion process. When they become worn, they allow oil to escape into the combustion chamber, resulting in oil consumption.
For example, worn piston rings can allow oil from the crankcase to get past them and into the combustion chamber. Valve seals, on the other hand, can allow oil from the valve stems to enter the combustion chamber. Both situations can cause oil consumption without any external evidence.
To address this issue, the worn piston rings or valve seals would need to be replaced to restore the proper function of the engine and reduce oil consumption.