That's good that he encouraged using math for real-life use.
I recall in the early 2000s, speaking with RX330 owners who told me they were averaging 18-20 MPG, depending upon the ratio of highway to city driving. I think even Consumer Reports listed that vehicle as having an average fuel mileage of 19. Ours has always been about 25-27 with a mixture of highway and city driving, but then again, it's a hybrid. The new Toyota Sienna hybrid vans are averaging about 30 MPG - fantastic for such a large vehicle that is not the best, aerodynamically-speaking.