Funny you should say that, I havn't noticed the smell I don't think (but I don't stand behind it
I can't tell you accurately yet and it probably *feels* like I am saving lot more than I am because the capacity is smaller (about 45 litres, instead of 70 litre petrol, and I always fill the tank so I can measure my economy).
I think I was on 28 mpg with petrol and now I am on 23 mpg, but the car is crying out to have the spark plugs and HT leads changed. I am impressed by how quickly the system switches over to LPG from petrol, which it starts on when the engine is cold. It gets warm enough for LPG long before the temp. dial moves.
Performance is dire above 4500 rpm - I expect it wants more advance... Perhaps they give it a nice "safe" map to avoid knock... After all it is not mapped properly, they just kind of load on some kind of default... but I am fine with this, if I want a boost of petrol I can press the button and it switches in literally 1 second
So when LPG runs out its like
"PETROL JUST KICKED IN!"
Most people don't convert to LPG because it does take a long time to pay for itself, but my attitude was: It's a new car for me, and the car was gloriously cheap to buy, so its an investment for the years that I will own it - and the resale value certainly can't go down any more! I even still have space for approx 12 cans of beer in the boot!