An update for Deet.
I filled the GS 450h (Gen 3 ) with Shell Super V and travelled from Wirral to St Andrews in Fife last Monday morning via the new Queensferry Bridge a distance totaling 290 miles.
I have covered 100 miles locally with School runs, trips to local Cubs and Rainbows groups and local shopping and have just filled up with 52.8 litres of Tesco Momentum.
52.80 litres divided by 4.546, gives 11.6 gallons into 390 miles gives 33.62 mpg.
My overall mpg over 55,000 miles gives 34.7 according to the OBC. If I assume a not unreasonable 8% error in the OBC, I arrive at 32mpg overall.
For a V6, providing a sublime ride in near silence with performance available whenever and wherever I want it , that is the "price " I pay.
The Gen 4 version is somewhat more frugal, but not ecstatically so, and I am sure that other members can provide their own stats.