Why is my Mitsubishi utility engine making oil?

By which, I assume you mean that the level on the engine-oil dipstick is rising, rather than falling slowly with time and kilometres. This is actually a bit more common than you might think and affects modern turbo-diesel vehicles with DPF filters.

In a nutshell, what’s happening is the vehicle is trying to 'burn-off' or clean its DPF filter. But in many cases, the engine and exhaust system never get hot enough for this to occur, so the computer instructs the fuel injection to squirt some extra fuel into the engine to get everything hot enough for a DPF burn. Inevitably, some of this extra fuel gets past the piston rings, into the engine oil and there you have the increase on the dipstick.

The problem is that this fuel actually dilutes the lubricating oil and suddenly, your engine is not getting all the protection it needs from the oil. The whole situation is a result of the engine not reaching a high enough temperature in everyday use, so the best advice is to make sure you take the ute for a 30 or 40 minute drive at highways speeds at least a couple of times a month. That will allow the DPF to burn off properly and you shouldn’t have the problem recurring.

For now, though, an oil change is good insurance against that oil dilution. And keep an eye on the level on the dipstick for future reference.