My Volkswagen Golf has been leaking oil from the bolts which go into the engine. I'm no mechanic and don't know the proper terms, but can anyone tell me if this is a serious issue and if it will need to be fixed? Check out the photo to see where the oil is pooling in the bolt recesses.
One thing to try is dip a the corner of a piece of paper into the liquid. If it's very dark black or brown it's likely to be oil, sometimes rusty water can collect in these orifices, and will look browny watery red on the paper, if it's fuel it will be clearer than oil, but you will be able to smell it as fuel.
If it's definitely oil, then if you have a access to a torque wrench you could try check the tension on the bolts are the correct manufacturers specifications. I can't comment on whether this will invalidate any warranty you may have. If they are correctly tensioned then I'd recommend taking it to a mechanic. If they are too loose, tension them correctly, soak up and wipe out any liquid that you can and dry out. Take the car slowly for a 5 min drive without over-revving, and then check again to see if the oil has appeared. If not, keep an eye on it closely for some time, ie after every drive for at least a week then once a week.
However having oil coming from this part of the engine doesn't sound at all good in my experience. Most of the oil is contained in the sump and splashed up around the engine inside.
The other option is the oil could have splashed or leaked into the recesses from being topped up recently. Has your car been for a service or have you topped up the oil recently?
My mechanical older brother commented that the rocker gasket cover can have bad seals and therefore can leak. This is less likely to be a issue as much as oil leaking directly from the engine itself, but it would still be very advisable to replace the seal as soon as possible.