So a little experiment in 'real world MPG':
I am doing Reading to Heathrow to Manchester Airport to Heathrow to Reading every Friday for next 10 weeks.
460 mile round trip, with 455 miles on Motorway. Early starts mean I miss most major rush hour bottlenecks on the way up, however Friday afternoons back down are always going to problematic with traffic.
Car is always 4-up, with correct tyre pressures. Car has had DPF de-cored, EGR pysically blanked, Terra-cleaned, an Angel re-map and only run on Shell V-Max Diesel with a 1ml/1litre shot of Diesel Rhino.
2 readings: One from the Computer and then one manually worked out by brimming the tank and calculating teh fuel used.
No clock watching , speeds of anything between 80-100 (Leptons, Officer) just keeping with traffic in the outside lane.
Real number: 36.2 mpg
Quite a shock if I'm honest!
Cruise control set at 75mph (just over 2K revs in 6th), Air conditioning Compressor Off. A very occasional blip upto 85ish to over take but then back on the Cruise control.
Real number: 44.6 mpg.
Getting better. This week, I'll try bang on 70mph which I think is a smidge under 2k revs in 6th.
Will let you know.