As I remember the company ordered about 6 Vectras on LPG,they did not come off the production line as LPG,but were then sent to Millbrook to be converted,I know I picked up the first one there,that 1.8 vectra used to return in money terms 43 mpg,on petrol she would do 32 mpg,of course the big 4x4's like Porsche,and RR's I suppose they would return mid 20's on LPG,you would think it would be promoted more as it is a clean fuel,if I bought at big 4x4 I would consider it but you do have to put the miles in to get the £1600 pound conversion.