As a newbie to the forum and to the Jazz, I have certainly found this long thread interesting and well worth reading. Although I’m in the fortunate position to be not overly concerned about fuel economy, fuel efficiency does interest me and i’m certainly interested in the question of the inaccuracies of dashboard displays and the reason why these errors might be present. The cynic in me feels that although legal it follows the VW saga, which has been proven not to be. I understand that the speedometer cannot legally read under the actual speed over ground but with simple software adjustments on our modern vehicles, especially with satnav, the odometer needn’t be so erroneous.
We had a 2013 Pug Partner Tepee for a couple of years and under even good long run conditions the 12500 mile countdown to service always threw the spanner light well under 9000 and that was on the odometer, the actual distance being somewhat less than that figure. We had a trip to Austria with that car and using our Garmin separate satnav and brim to brim fill ups for 3000+ miles, the actual mpg (diesel) was a shade under 54 whereas the display indicated 59.2.
My Daimler SV8 with a 4 litre Supercharged engine, weighing in at over 2 tons and with 370 willing horses achieved a properly calculated 25.1 mpg on a recent trip to Germany, which might alarm the tree huggers but that IS fuel efficient.
By the way, I was not born cynical, it only started when I was two 🤓
Regards,
Ian