Engine Burning Oil problems of the 2006 Lexus IS350

In normal driving situations my 2006 Lexus Is350 burns oil very quickly. I am adding oil at least every 3 weeks (about a quart or more). There are no specific engine leaking issues per my mechanic. The engine seems to burn oil abnormally fast.

Oil consumption. Vehicle has no leaks and needs 1quart of oil added every 2k miles. Car has 150k and has been well maintained. It uses valvoline 5w-30 full synthetic oil and gets changed every 4-5k miles of oil usage. I've read many complaints about this issue and Toyota/Lexus is not willing to help out with this issue.

Engine is burning oil at a rapid rate. It requires 2 to 3 quarts of oil every 5000 miles.

Excessive oil consumption. Started around 120k miles.

The vehicle's oil consumption is becoming greater and greater. I am now at a point where I need to add 2 quarts of oil every 3 weeks, which is about 1000 miles driven. Because of the age of my vehicle, I was advised to start using synthetic/blend, but the oil consumption rate has not changed. It was inspected for leaks and there were none. Does this have anything to do with past recalls? I know this is not normal and I am hoping for a resolution as I love driving the car and it still feels reliable aside from the oil consumption rate, which is getting worse and worse. I am now on my third case of oil purchased from costco but once I'm through with it, I'm dreading the rate will be much sooner- I don't want to have to add oil every week. I'm hoping for a resolution/advice. Thank you.