Have just got rid of my IS220d and the overall average over 101,000 miles was 38.7 mpg (according to the car). Have just bought a GS300h with 38k on the clock with an average of 42.2. Went for a long weekend in Belgium over Easter in it, did about 700 miles(mainly motorway - or whatever they call them in Belgium) and the average over two tanks of fuel was 45.6. Best I've seen so far was just over 50mpg on a tank but that was as boring as hell! I think the IS300h has basically the same engine and it's a bit lighter. I do agree though that if you do plenty of town miles the electric motor and engine cutting out when stationary really improves the mpg.