sorry guys!! been extremely busy with work.. beside that, I really don't think it have anything to do with the gas because all I pump is shell gas.. I'm planning to start with an oil change and see from there.. i talk to my mechanic and he told me that a lot of the Toyota vehicle make this sound eventually overtime.. This is my second Lexus but I never had a problem with my first one because I bought it off the lot.. I talked to the previous owner and he told me that he just change the crank pulley, timing belt, and etc. but you cant believe everything you hear..

 

Regardless of what station you use, you should still run the manufacturers recommended octane for your vehicle. Correct me if I am wrong, it is premium for the IS300s right?