Hi Mike
It is more complicated than leaning the mixture a bit - there are commercial ECU remappers who advertise a 20% improvement in fuel economy if you have them work on your car.
I put an external chip (connected to the ODI port) on my car for a few months and it had minimal effect - it just seemed to get hot so I removed it.
Bren
Hi Bren, I seem to remember one of the main TV channels did a programe reviewing many of these Snake Oil products some time ago and not one of them worked. They came to the conclusion that if it was possible manufacturers would have included it in their building specs years ago. Mike.
I think you'll find that many manufactures were going to supply new dual fuel cars this included Land Rover who about 6-7years were in talks with government The government, in their wisdom, discouraged the idea because if other manufactures followed suit & it caught on with the public (which it would) it would mean a substantial drop in tax revenue. The only manufacturer who I recall did offer dual fuel was Vauxhall but they have dropped it
Volvo & Saab also offered it and you right about the U turn the government did, their loss our gain.
Mike
Ford, Proton, and Nissan as well I think.
I certainly had a Y reg Primera that was an official conversion, though I believe they came off the line as standard cars, and the conversion was contracted out.