I have used Toluene, and Xylene as an octane booster. They are 2 additives that are commonly found in race gas, and in injector cleaner.
The IRL was using them almost very high percentages 80-90%
Do some research on the net.
There was a long thread on a 4wd forum (all in spanish though) about acetone in those percentages, almost everyone got an improvment of about 8 to 10% on fuel economy. One of them even tried it secretly into his wife's car to see if fuel was an improvement and if she would feel a difference. (and it actually did)
On the ones that were getting 7k's per liter it did nothing or almost nothing, (old 2F engines) it was more noticeable on the ones that normally were getting over 10 k's per liter of fuel.