just go into auto1 and look at all the wynes and nullon (no idea how you spell them) bottles and just read the back to see what they claim they do, then buy the one you like the most.
Inter-Ject-Ron is highly recommended by my mechanic (my dad).
Works well with most engine types.
Sold in a tall white bottle about 200mL. Good for one tank, but is supposed to last 2 or three. I just add one every now & then when I remember.