I have some photos of a 2000 Honda Civic engine with 140,000 kilometers
(87,500 miles). 98% of them local, urban miles. Fuel has always been a
95 octane. Engine oil has always been synthetic (in this part of the
planet) but changed every 10,000 km (6000-7000 miles) anyway because all
the driving is local and in high stress traffic.

Photos: http://drop.io/OilyHondaEngine
[note that image size is 2048x1536 pixels, and the website preview is
too small to see detail; click download to see orig rez]

I noticed too much oil around the engine surface recently, a burning smell
coming from the front. Don't notice any smoky exhaust at all, although
the noise from the exhaust isn't as quiet as it used to be (although not
at all excessively noisy).

Photos (some taken with flash, others no flash) show heavy oil buildup
(with lots of dirt) in bottom/crankcase part. The borderline of oil on
the valve at the top seems to show even (horizontal) line a few
centimeters above the main engine block. No real noticeable loss of
engine power (compression?) problems.

Putting it all together, potential problems suggest:

* worn-and-torn gasket or seal between valve cover and main engine block:
I consider this most likely problem, since the horizontal line of oil
suggests this, and the leak of oil would eventually cover the whole engine
block

* worn piston rings: wholly unlikely, since wouldn't that cause a heavy
smoky exhaust, and why would oil leak out of engine

* some other seal or gasket problem? in addition to the problem I
indicate above? I will probably only be able to learn this after having
one part replaced and then somehow cleaning the entire engine block free
of dirt and oil...how to do this easily?