Nah .... I had my van converted to LPG a year ago .... it was a costly outlay of about £1k, but one which has now paid for itself with what I've paid in fuel, plus the van is now worth an extra amount of around the cost of the conversion because it costs half the price to run compared to petrol.
If you don't 'buy' petrol or diesel any more for your van I hope you don't syphon it out of other people's vehicles!
It's changed a van that I felt hesitant to drive because of the fuel costs (it only does around 20mpg) into something I'm happy to drive at any time, and it actually costs me less in fuel than the car it replaced when I bought it. And on top all that, it's a far greener fuel.
It's one of the smartest things I've ever done I reckon.