It's been a while since I've mentioned my experiments adding acetone to my trucks fuel tank, so just to prevent you thinking I'd given up on the matter, here's an update. I've improved the algorithms I'm using in my Excel spreadsheet because I was bored, so now I compensate for remaining acetone as a result of refilling before the tank it empty, volume of acetone added and I get rather more informative analyses. Additionally, I've added a more data points, putting me at 17 tanks of fuel on the chart. Currently, data suggests a near linear economy increase for my truck of about 7% at 0.15% acetone concentration (1MPG at 1/3 cup acetone). This linear increase isn't showing any signs of leveling off, so I'm going to start pushing the concentration up in the next few tanks. I'll give you a better write up with more manageable units when I'm satisfied that I've found the acetone concentration of maximal economy for my truck. I expect that I'll probably repeat this experiment with my next vehicle, and every vehicle thereafter for that matter (as long as they still run on petrol).