Actually this isn't done by ourselves but by one of the few garages authorised to make such conversions. LPG has many advantages:
It's cheap. In almost all countries in Europe LPG is far cheaper than the cheapest unleaded fuel. In many countries like Belgium, the Netherlands or Luxembourg it's 1/3th of the fuel price.
It's clean. Your oil will be happy much longer as LPG has almost none polluting parts. You can extend your oil change by far and your oil will still be clean.
Improved cold starting. LPG does not condensate in cold cylinders unlike fuel. You have almost the same performance with cold engines than with hot ones.
Improved range. Normally you keep your existing fuel setup unchanged with the exception of a small solenoid in the fuel feed line. Gas installation is added and depending on tank size you can double your range. Useful on those long hauls.
LPG works very well with modern engine management systems and catalysers.
It's safe. LPG tanks are incredibly strong, made of heavy gauge steel and tested to 100 times standard pressure. I saw Range Rovers with gas tanks under the drivers floor who crashed on stones offroad with the tank. The stone broke- the tank was not even dented.
Disadvantages:
You need to free some space for the gas tank. They come in various sizes but they all take up room. This may well be a problem on 90's or Freelanders. And you may only fill the tank to 80% for safety reasons (automatic valve). So an 100 liter tank will hold 80 liters of LPG.
Gas has a lower calorific value than fuel. This means you will burn about 5-10% more gas than fuel.
Older setups did loose some power when running on gas. New ones had this problem eliminated. In fact, most run better on gas than on fuel.
In many countries LPG is not readily available. Check this first before launching you into this.
Some governments have an special tax on LPG vehicles- no one knows why (surely to extract that saved money again from those silly suckers…)
LPG-vehicles MAY NOT use an oil bath air cleaner like the elder series vehicles. K&N filters are ok.
Important: You MUST first check your legal legislation if it permits the fittment of LPG by an approved garage in Luxembourg. Though our safety legislation is among the most stringent in Europe it may not correspond with your rules.
No do-it-yourself kits available.
Prices:
As an example an LPG conversion on an carburated 3.5 Defender runs around 75.000.- Flux (3.750.- DM). About the same price was asked for converting an 3.9 EFI Range Rover. Count on more if you wish special details like double LPG tank or special long range tanks.
Installation time is about one day.