New 4runner owner w/Tapping in engine

Hello all!
I just recently purchased a 93 4Runner SR5 rwd w/ auto trans. I have never owned one before and I am not sure if my experiences thus far are normal so I want to ask the experts; other owners. I have a slight tapping from the engine that sounds like lifters but do not know enough to say for sure. It occurs while cold and hot, park and in drive and anytime the engine is on frankly. When I bought it, it appeared to have fresh oil according to the dstick. But today, I noticed the oil guage operating in the low range so I checked it; it was bone dry...I added three quarts! I have not seen any leaks of any kind. The tapping is not any worse afterword. A stranger who claims to have had a 4runner in the past stated that the noise is normal but I am concerned. The engine is rock steady even under load and does not appear to be blowing smoke. Any thoughts???

I put Dura-Lube in mine and it seemed to get rid of a lot of the tapping... From my experience the stuff works pretty good..