actually, i'd like to tell the same as others saying - when you are driving actively and "sharp" - the consumption can be twice worse than you are driving "carefully" - this is real life and no any magic...
for example - you can drive at second gear 30mph and your car will be really fast-responsive (like a "sport" mode in auto gearboxes), but you can drive 30mph on the 3rd gear (like a "normal" or "economic" mode) - and is will be not so "reactive" but much less diesel-hungry...
Anyway, it is a really good idea to check your 5th injector even on the new car... Personally i think that this is a manufacturing problem and they are (lexus) still fixing it only in services
12000 mile 90%urben 10%m way had the ecu change dont know about 5th injector 26-27 mpg but i do run at just under 2k revs (thinking of hummer next to reduce the fuel bill)Had all the other faults but when reported they have all been sorted so maybe this will next month at the service.Still a better car than the usual bmw/merc/audi .love it