I'm not really discovering that many drawbacks. I have a really small fuel tank, but that's my fault for being lazy and not wanting to chop up the rear of the car and mount a big tank.

LPG at 12:1 is perfect. I was always planning on going turbo once my registration problems are solved.

Worst drawback: 0.3 less energy per gallon and you have to 'find fuel'
undecided: fuel is 1.95/gallon and always full serve.
Best thing: More BTU/LB than gasoline

i am getting 15.5 MPG on lpg at the moment. Not great, not too bad. I've just been trying to get my calculations refined so I can plan fuel stops.

currently LPG is cheaper than petrol even if i use 1/3'd more. I'm saving about $0.04 per gallon now.

I'm still learning how propane behaves differently. The octane is high enough that you can idle around town in 5th gear and the car is happy. No acceleration, but it'll put from light to light.

I'm currently trying to not be a hoon and see how it goes if I keep the rpms down and don't mash on the throttle.

the range is 15 -17 mpg ( 19.5 - 22.1 petrol mpg - not too bad ) So far.