Welcome, it's worth checking to make sure that your Lexus has had the remedial work done on a recall about 4/5 months ago. A phone call to Lexus or a dealer should give you the answer.
Since I had the recall work done my onboard computer is showing around 26.2
A few members on here have experienced the same, my car is in for it's service the end of this month so I shall ask them to check this out. It was averaging about 30 so I hope to get this back.
One other thing, have a very close look at the alloys, they are very prone to blistering, if they have this negotiate on the price or at least get your seller to refurbish them!
Good luck