My 2002 Mazda Tribute with a 3.0l V6 (200K miles) started making a knocking sound a couple of weeks ago after an oil change (5W20). The knocking happens when the engine is cold and idling and is intermittent. It seems to go away after driving the car for 10 minutes. The car drives just fine. I tried adding Seafoam to the oil. I also tried filling up the gas tank with supreme gas + Seafoam. Neither solution helped. I later tried adding Lucas Oil Stabilizer, which seemed to quiet the knock down for a few days, but now the knocking is back.

The knocking sounds a bit too low to be the lifters, but I'm not positive. I've attached an mp3 sound recording of the noise cutting in and out right after starting the car first thing in the morning.

Any suggestions would be greatly appreciated.

 

What grade oil where you running prior to the oil change?

 

First stop trying to stop the problem chemically .

You changing the oil (indicated 5w20) really had nothing to do with the sound now and only a coincident that it started after several mile from changing the engine oil.

You need to isolate exactly where the sound is coming from. The way to do this is using several methods to find the sound and identify it.

You can purchase one or make one using a Philips driver, 1 foot of vacuum hose and screw or bolt.

Once you find the location of the sound we can better suggest what the sound might be.