I've just completed a run until the LPG ran out. I got 290 miles. It then cost me £36 to brim. So, considering the difference in cost, I guess that means I'm getting the equivalent of 46mpg. Hmm, could be better.
Thats 49.4L (11gal) of LPG to cover 290 miles, 26.6MPG ave
That doesnt sound too far off, the TT is not a particularly economical car at all and LPG will never match gasoline. Coming from an Insight though it will be heavy on the wallet even if the fuel is only 72.9ppl