You always want to follow the owner's manual. However, if for some reason you can't, you can use regular. However, it can cause knocking (maybe not -- German cars do that), a lower fuel efficiency (I once did some calculation and found on some SUV it was better to pay more for the premium, lol), poorer performance, and premature engine wear. You should talk to some mechanics at your local Lexus dealer. Those are the people who know what the consequences are!!!
