Mini One potential VANOS issue

It sounds like you're on the right track. The check engine light and higher fuel consumption are definitely indicators of a potential VANOS issue. Since you are familiar with a defect in one of the camshaft solenoid valves, have you checked the oil condition? Sometimes oil sludge can cause these valves to malfunction. Also, have you confirmed that power is actually reaching the solenoid?

Thanks for the quick reply. How would I check the power supply to the solenoid valve? And regarding the oil sludge, is there a specific place I should be looking for it, or just generally inspecting the oil during a change?

Checking the power supply to the solenoid valve usually involves using a multimeter to see if voltage is present when the engine is running. As for the oil sludge, it tends to accumulate in areas with poor oil circulation, such as around the camshafts and within the VANOS unit itself. Given the potential for oil sludge and the need to test electrical components, I would recommend taking it to a trusted workshop that is familiar with MINIs to diagnose the problem properly to avoid a VANOS failure.

Thank you for the helpful advice. It does seem like I am not equipped to handle this myself. I took the Mini One to a workshop, and they confirmed the inlet camshaft solenoid valve was indeed faulty. The repair plus the part cost exactly 250€, as predicted. Now the check engine light is off and the fuel consumption is back to normal.