Alright...Mazda 97 626 LX, ~103k miles on it.
Head Gasket was replaced in 2002, and it was working like a charm. I only mention this now because, over the last few months, my engine has slowly begun to sound worse for the wear. To be frank, it sounds like a miniature version of a deisel engine when I turn it on (it is a hard sound to explain...almost has a 'splat' like quality to the sound).
Recently had general maintenance done on it (oil, tires, blades, etc., and techs said they didn't hear a thing relating to the noise), and it came back sounding alot better. Three weeks later, it is worse now than it was prior. However, the noise is also sporadic. Will be driving, with noise and, a few miles later, there won't be a sound in the world to indicate that there is an issue with the car. A few miles later, back to making that noise.
Within the last week, the fuel economy has dopped by almost 30% (before it was 140 miles at 1/2 a tank, and now I'm down to 100 miles), and the oil light is coming on sporadically.
As far as the oil light goes, it is coming on during acceleration, and sometimes during normal operaiton. Very sporadic, sometimes it is very dim. When sitting at stop lights, it usually shines the brightest when it is on. I am guessing It is either 1) loose sensor, or sensor going bad, or 2) the oil pressure is dropping, thus the indication that something is wrong. I believe that the noise coming from the engine, possible air leak (it's not quite a knocking) is coming from around the injectors/ right hand side of the valve cover (near the oil cap on the top of the engine).
Temperature has remained normal, and I have gotten into the habit of checking the oil before driving off, and as soon as I arrive (for any appreciable differences). None so far except that the oil seems to be a dark amber color after only going 1300 miles (not sure if that's normal, that's why I'm throwing it out there). Any pointers would be greatly appreciated.

-JP

 

I have had two Mazdas and a Ford truck that i had to fix with this similar problem. It also had the oil light on like this too. What happened was that the oil pump pick up screen gets clogged with carbon and needs cleaning up. I removed the oil pan and pick up screen to clean all the residue that settles at the bottom. When starting the engine it sucks all the junk against the screen and starves the engine of oil. When turning it off the junk settles back to the bottom of the pan. When removing the drain plug not all of the oil drains.