being a 2010 model the hybrid battery will need replacing soon
lexus warrantys the battery for 8 yrs or 160K kms which ever comes first
the RX450h should be averaging around 7-8L per 100kms
i had a this problem in a customers LS600h and after the battery change it went down by 4ls
new battery installed from lexus was just under 6K
so a RX450h should be abit cheaper than that