Now I remember why I decided to go Petrol!
Unless you're doing huge mileages what you save in fuel rapidly disappears with Turbo failures, DPF problems, swirl flaps, injector problems etc
Not sure about the 159, but there's probably space for LPG and generally the experience is fine.
I have an elderly 5 cylinder V70 auto that does 20MPG - but the LPG means it costs me about 15p/mile not 25p
I'm considering it on my 166, but I only do 5k a year so it's marginal - especially at 97p a litre for petrol..
Good luck with your search!