Interesting you should bring up the aircon stuff. I've checked on my 1.9 a couple of times...motorway speed, flat road on a fairly warm day (around 40 degrees) and she's drinking 4.1 l/100...turn off the a/c and reading drops back to 4.0, so it makes very little difference. Headlights must be lit at all times, so they are no factor for me.