Is this normal? Avensis T27

[Avensis_11]

Please see the oily mark in the photo below?  It is not a dry mark.  Does it indicate a problem?  I have had to top up the coolant twice in the last few weeks, which I know isn't normal.  Could the 2 issues be related.  Car was serviced last month with no issues reported.  No obvious evidence of a leak when I look at driveway where car is parked.  Drives fine, no power loss and isn't over heating.  It's a 1.8l petrol 2011 Avensis with 73k on the clock.  Mostly used for motorway runs.

[Konrad C]

My '58 ('09) Valvematic has not lost any fluids. Coolant and oil checked regularly and no top up since oil change. I will look for make and stains and take photos. 
When I had my old ('98) Avensis, it had a very hard to detect coolant leak, which I found by accident - the top plastic section of the radiator had cracked. Replaced that with a few hours of discovery. Even with the leak, the car never overheated. Same when the water pump went in that car and my old Cavalier. 
The best time to  look for any leaks is when the car has been switched off, and cooling down. Take the engine cover off and look down the drive belt side under the alternator.

I will look at mine later and post back when I have time.

Edited February 9, 2018 by Konrad C
rearrange sentence

[Konrad C]

i had a look at my engine and everything looks normal. It is the cylinder head cover gasket.  

I took the engine cover off to show the engine

The marks are exactly the same.

I checked the oil and coolant levels.  They are fine.

If you suspect a coolant leak, check the pipes, radiator and water pump area. The water pump is just below the alternator.

Look at the under engine cover for signs of fluid. it should be dry.

[Avensis_11]

Thanks Konrad.  Good to know the oily marks are normal.  I am monitoring coolant level closely (after last top-up).  If it drops again with no sign of a leak I may replace the reservoir cap.  If the seal at the cap isn't great - perhaps coolant evaporates as it gets hot?  Or is that a waste of time?

[m456an]

It would be better to change the radiator cap