I get 20l/100k towing a car trailer with a car on it. It did 25l/100k with a LWB 2A Landy on the trailer, and they are not light. Ignition is advanced to 12 degrees BTDC. This is not the injected system. Has not backfired since I fitted a new MSD coil and new leads. It took me a while to find a good LPG bloke in Brisbane as most of the "Experts" set LPG systems up to run rich so they do not backfire, which sort of negates the advantage of running on gas. Car trailer has hardly been off since xmas so I have not done a D1 only run for a while. It did 14l/100k last year.