Re the engine temp on lpg as related in that article, it makes no sense to me at all.
1. LPG has a lower calorific value and burns at a lower temp
2. Just because it's takes micro-seconds less to flame and therefore expand does not in itself create more heat.
3. It is of a higher octane than petrol which means the engine can run on different timing, if required.
Bottom line real life experience seems to be that LPG'd petrol engines work well enough, but lower power and lower mpg.
They always give lower mpg and even when taking into account the difference in price per ltr between 95 u/l and lpg in France:1.52 versus 0.90 does not show lpg as half the price of petrol.
So, taking into account a lower mpg on lpg plus the fact that lpg is not as cheap relative to petrol as it was, I can't see it stacks up. Then if you take into account that an lpg-equipped car has, by definition, 2 complete and separate fuel systems, you have double the possibility of problems.
So what's the advantage of a V8/lpg Disco? Yes, it is more powerful by comparison to a TD5 in std trim - but the TD5 can have it's power and torque increased significantly at really quite low cost. A TD5 remap from a reliable source can be effected from as little as £225. This will increase power from 136bhp to about 160bhp with big gains in torque, particularly in the rev range 1500 to 3000rpm.
Just my 2 penn'th