VBdenny... I do reside in the So. CA area, and we seldom experience any cold weather that is worth mentioning. I did switch to a Synthetic Blend engine oil to extend oil changes some, but for no other reason.
There seems to be a consensus that the noise is due to the fuel injector system. I have no way of determining if this truly is the cause or not? Some say that they were told by Lexus dealers that the fuel injectors were the culprit, and not to have any worries, as this noise is normal.
I'm definitely not going to pay a dealer any money to correct this problem, as long as it is harmless. The RX350 is a fine auto, and you would think that Lexus would create some sort of recall to correct this noise, but my guess is that the fix would be very expensive, and Lexus is reluctant to have a recall for this reason?
I have yet to contact a dealer about this problem, but I may do that to re-confirm that the problem is with the fuel injection. I really have no reason to doubt that the members that have made comments are not being truthful about having contacted Lexus dealers.
DBTED