Engine oil is at max limit, also when engine is cold there is no noise. this is not new, I've had it for about 15K miles. I have now 60K miles. No apparent side effects, and tapping has not gotten louder or worse than what it initially was. if I rev the engine (parked) slowly, the tapping stays, the noise though subsides momentary if the engine is rev'ed suddenly. I heard other 3series cars in the same model period have the same tapping noise.. but there are no recalls related.. The noise bugs me. One mechanic gave me an off the cuff response, that BMW service interval is too long and causes such symptoms to exist in the 1st place. He did not recommend any engine cleaners though.. I am planning to sell the car some time this year, and worry more about potential buyers devaluing the car or worse not buying the car.. any tips and recommendations are greatly appreciated.
Engine tapping noise when warm, idle, parked or low speed. on 2006 BMW X3
His "off the cuff" response is 100% correct. 15K oil changes cakes sludge inside the engine, also restricting oil passages. Try http://www.lucasoil.com/products/display_products.sd?iid=49&catid=7&loc=show&headTitle= - Lucas Synthetic Oil Stabilizer with some fresh oil
agree with #1 completely