I have a 2014 Mercedes-Benz A180 and have lodged an insurance claim with NRMA as the engine in my car has a broken valve spring. The only way the Mercedes-Benz Service Centre discovered this was to take the head off the motor. NRMA claim it was dirty fuel, is it best to use 95-octane fuel or 98-octane Fuel. Or would you know what other thing may have caused a valve spring inside the engine to break? It has only done 96,078 km.
A broken valve spring is not something that would be caused by the fuel. Most likely the spring was faulty, perhaps there was in inclusion in the material it was made from, or there could have been some other manufacturing problem. Use either 95 or 98-octane fuel.