The engine oil warning light as seen in the image is displayed on the dashboard. The light has recently come on and doesn't go off after starting the car up.
The engine temperature reading on the dashboard gauge is noticeably higher than usual. It doesn't seem to be caused by sitting in traffic on a hot day, it is generally just higher all the time.
There is residue from an oil leak on parts of the engine around the crankcase.
When the engine is running it does sound like it would normally, it can sound like it's struggling to keep running or produce strange noises that sound like it's not running in time with itself.
There appear to be fluid patches underneath the car when it's been parked up for a while.