Assume you mean the engine oil level on the dipstick is getting higher?
I would be surprised if it is hydraulic oil (unless you know different) but I suppose diesel fuel is a possibility though it is many years since I have heard of such a thing, especially if the engine is otherwise running smoothly. The last time I saw that was on a small diesel engine with a conventional dpa type injection pump driven by oil-fed gears. The pump had sprung a leak and begun to fill the engine. There was no mistaking the strong smell of diesel...
An internal coolant leak can have the same effect but without the smell of fuel.
Answers & Comments
Assume you mean the engine oil level on the dipstick is getting higher?
I would be surprised if it is hydraulic oil (unless you know different) but I suppose diesel fuel is a possibility though it is many years since I have heard of such a thing, especially if the engine is otherwise running smoothly.
The last time I saw that was on a small diesel engine with a conventional dpa type injection pump driven by oil-fed gears. The pump had sprung a leak and begun to fill the engine. There was no mistaking the strong smell of diesel...
An internal coolant leak can have the same effect but without the smell of fuel.