I would never buy a loaner or rental car. I have never purposely abused a rental or loaner, but there have been the occasions when I have said "oh well, it's a rental".
Look for a good used RX. I just tried to trade my 04 RX330 with 50,000 miles on an LS. I know they were not overpaying me on the RX because I did a lot of research on the price of the LS. They offered $23. Another dealer offered $22,500.

I would think you should be able to buy a nice RX for around that price from an individual.
If the new body style RX were out now, I would sell my RX for $25+ to an individual. I have to cover my sales tax loss. Kansas laws subsidizes dealers. The only way to pay only the sales tax difference is to trade the old car in on the new purchase. Rip off, but nothing I can do about it.

(I didn't buy the LS because of not great posts in the snow)
ralphj

 

Service loaners can be a bit risky, even if it is a Lexus. Who knows what kind of gas people put in there before returning the cars. I know I don't treat loaners as well as my own car, especially when the dealer's holding mine for a week because they screwed up service and needed to order replacement parts...twice. Maybe try an off-lease?