I have tried a couple of different ways.
1. Brim to brim on filling as well with note of mileage.
2. mpg thingy on MB dash read out.
3. iPhone app speaking to ELM toggle thing attached to OBDII port
The differences were around 10-15% so I did a couple of journeys using all of them.
This was on the ML63 with a V8 lump with a severe petrol problem, changes are easy to spot on lower numbers
Brim-Brim 20.4mpg
The car's own MPG display 19.7mpg
OBDII 20.2mpg
I guess the Brim figure can change with heat, nozzle etc. I was surprised the car gave a lower figure than the OBD given they must be using the same data? Maybe they don't want mileagegate?
I am guessing that they use the engine management computer to follow the petrol injection information? So if the tyres are wrong or inflation out it could make a difference.
Either way I need to get less well acquainted with the loud pedal.
Thank you that has made me feel so much better with my 23mpg, brim to brim with E5
Keep the faith
keep it planted
