If it's any help - I took delivery of a new Premier in May on 16" wheels. I have recently started doing a lot of business miles, from Leicester to Newcastle and back on the A46 and them A1 so mostly 2 lane dual carriageway. I am using normal mode all the time, doing 70mph where possible (mostly averaging 55mph overall) and am now returning about 60mpg. The car has now done 3000 miles. I have had diesel estates for the last 15 years and although the Lexus performance is not as good, I find it acceptable and the refinement is much better, the lack of NVH is remarkable.