In terms of LPG, all I can say is don't. I was considering having mine done. I contacted five different companies, who all told me five different things with all the advice differing from one company to another. I have heard of LS430 owners having no problems at all and other owners who's cars were plagued with problems after having an LPG system fitted. If you want economy, and I really hate saying this, BMW730d, Audi A8 3.0tdi or Mercedes S320CDI.