Is it possible to mix water and gasoline? If so how do you do it?
I have to point out that a well known gasoline/water emulsion is napalm. While I think you want to make an efficient fuel, water expansion at engine temperatures is phenomenal (about 1400 to 1) and was used in the P-51 mustang fighter planes to nearly double the output power. However, those engines has a service life of about 30 hours in that mode. Here is the issue, while I am very happy to provide help to responsible people in such endeavors, I cannot verify the safety or responsibility of the people involved.
Many people have been hurt or killed by vapor explosions, and gasoline is a classic vapor explosive in air. Gas/water or worse gas/alcohol mixtures have substantially lower vapor pressure --in fact gasoline and tert-butyl alcohol will boil at 70F.
On the other hand, I think this line of questioning is very interesting and would make a good science fair project.