I have 2 experiences of LPG.
When I was still in the police in 2001- 2002 I regularly drove anAstra that had a factory LPG conversion which we were testing.
At 50,000 miles it had a cylinder head gasket failure which our workshops attributed to the hot running of thegas conversion.
The engines run hotter on gas, you have to start on petrol and then the car switches over automatically.
The performance is affected quite a lot when running on gas - the Astra was a police spec car so had basic trim but SRI Recaro seats uprated brakes and suspension. If I was in a rushI immediately switched to petrol to get the performance. Don't forget you can't do a direct mpg comparison, the gas tanks either take up boot spaceor the spare wheel well.We certainlydidn't continue trying them and in fact soon after switched most of the fleet to diesel Fusions (they are still buying them now).
My brother in law used to be a fleet manager at a Vauxhall main dealership about6 years ago which decided to do LPG conversions. They did them on all sorts of vehicles not just Vauxhall.The workshop manager had a nervous breakdown because of all the problems with the converted engines.
I suspect your new car warranty would also be invalidated in respect of any engine related claims minimum.
Personally I would leave well alone and change the vehicle for a diesel ifI was looking to save fuel costs.
57 Titanium 1.6 110 DPF, X Sport pack, panoramic roof,Sony 6 CD changer with voice control bluetooth.