'01 Mustang GT ran low on oil. Valve cover gaskets to blame?

Checked on my fluid levels since I had a ton of smoke come out of my engine a while back (back of the engine bay on the passenger side), and found both coolant and oil dangerously low.

Filled 'em up both back up, and didn't come across that issue again (but my radiator went, as some of you may know). I wasn't able to find a leak with a cursory glance, nor did I smell or see symptoms of oil being burned.

I had my mechanic check it out, and told me that the valve cover gaskets were both bad. Is it possible for oil to excessively leak from there without notice, or is there something worse at bay that I should be checking out? It's an '04 engine with 100k-ish miles. It doesn't really sound like it's knocking either (random note that may or may not connected - oil pressure gauge has been out since the engine was swapped).

Say it's the gaskets - any brands I should actively avoid? Seems to be a bunch with Fel-Pro leading the way

First things first.

Put an oil pressure gauge on it.

No no, I mean the gauge is still a part of the cluster but it's totally dead while all the others still work (battery, temperature, speedometer, tachometer, etc.)

Maybe pull the dipstick occasionally.  Felpro gaskets will be fine, but if the oil level was "dangerously" low, which I would take to mean 3 or more quarts down, you'd have puddles everywhere from a leak. 

It's burning oil.  Check the oil often enough to figure out how much, then top off as required.

In reply to Dootz :

The gaskets will not cause it to lose oil as drastic as you described. What will is the valve seals. Im not sure if it smokes at all while running but does it smoke on start up? Sometimes they start to go bad and allow oil to drip into the cylinder over night and it will cause smoke on start up. 

Other notorious seals that go bad are the oil cooler and rear main. 

Valve cover gaskets can 100% cause it to leak and then drip onto the manifold causing it to smoke, but i have had probably 25+ of these cars and never seen on lose quarts of oil as a result of it. 

When you do get gaskets just make sure you get the right ones. Ford used a variety of different valve covers in those years. Some being 9 bolt and some being 11. Some of the gaskets have sections to go around the bolt holes and some do not. 

Sounds to me you have a cracked piston. It’s clearly using oil and combustion gases are pressurizing the crankcase which is just manifesting as bad valve cover gaskets.

If it were the valve cover gaskets, you would have multiple quarts of oil draining outside of the engine.  Which is pretty easy to notice.  Are your engine, trans, and underside of the vehicle totally covered in oil?

Low on oil? Sounds like a 4.6 to me! I just add a few quarts every few months, or whenever the oil light blinks on under braking. (I'm a dumbass, fwiw)