I am new to the form but I am very concerned with my 2007 Lexus RX350 I just purchased. It has 35,000 miles on it and was 1 owner by an older lady. Jumping right in the engine taps while idling or accelerating after it has warmed up. I didn't notice the noise until after I bought it. She had regular oil changes with conventional oil, and she apparently used 87 gas. When I got it, I filled it up with 91, changed the oil with Mobil 1 5w-30, changed the air filter, and put in fuel treatment since the car had been sitting for so long. I have burned 1 tank of 91 with fuel treatment, and just added Sea Foam to the next tank. I have driven it about 200 miles. It taps real bad when its cold but gets quiet. I can still notice it while accelerating but not as much or at all when idling.
My questions are: Did the old lady permanently damage the motor with 87 gas? Does using synthetic oil cause this when switching from conventional? Will the noise go away?