Thanks for the response. I did replace the PCV valve early on and the tube to the intake manifold. Recently, when the valve cover was off I traced the hose and attempted to clean out the fitting at the base of the carb. Is the remainder of the system in the throttle body? Any other areas to clean that you know of? My air filter is oiling up quickly requiring frequent replacement but it always seems to have done that- possibly a bit worse recently. The little pre-filter on the aircleaner body oils up quite quickly. Any other areas which effect the crankcase ventilation system that I might check out?
Hmmmm. I didn't know about the excessive oil buildup on the filters. How many miles are on this engine? Do you have to add oil regularly? When you had the valve cover off, did you see alot of black buildup inside the valve cover? If so, was it around one particular valve or area of the cover? It sounds like you've got some pretty bad blow-by, bad rings, or maybe one of your lifters isn't sealing well enough, sticking, or something. In any case, it may be time to consider an engine rebuild or picking up a good engine (under 170,000 miles), if you can find one, at local salvage yards. It sounds like internal engine components are resulting in increased pressure which may be contributing to your valve cover gasket leaking like that.
On the other hand, before tearing out / tearing into the engine, the easy thing to do is just try to get those semicircles to stop complaining for now (as you were doing originally) but if the crankcase pressure is high, you're going to be plagued by leaks here and there until you overhaul that engine. The whole point being, the pressure is more than what the engineers expected that engine to take on, so all the seals aren't going to be made to handle the pressure - oversealing one area just sends the pressure to another area. With all that oil buildup, your PCV system is almost surely suffering at some point.
If it were me, keep in mind my standards are low as far as cosmetics go, I'd throw an old cardboard box on the driveway under the front end of the Mazda to soak up any oil drops, and just let it cry a little oil, as long as it wasn't so much that it affected other components. For instance, if it gets on the belts and whatnot, it'll spray all over the engine, foul out the alternator, etc., but I drove my previous Mazda for years with a tiny oil drizzle onto the exhaust manifold that didn't affect anything else. Personally, I find oil consumption of up to 3 or 4 quarts between oil changes (@5,000 miles) acceptable. But that's me.