the best i can describe it is when im at a low speed, occasionally i will hear the slight tap. almost the same sound as if you take a ball point pen and click it several times in a row.
I changed the gas to 89 octane to see if it really does do something.
As for the oil. its changed every 3500 miles. the next oil change in june, i will be putting Mobil 1 synthetic in. the car has 100k on it.
I just tuned it up in january.
can you try to give us a really good idea of exactly WHEN this occurs? While coasting... while accelerating, while lightly accelerating.... can you replicate the problem in park/neutral by gently revving the engine? is the engine warm, or cold?