[DrBob]

Depends on what you mean by "work". Yes, they will, in a lab, somewhat 'work' in that the tin (and sometimes aluminium and silicon) in them helps break down longer hydrocarbon molicules into shorter ones. However, here in the real world they show very little in the way of benifits, because modern engines effectively burn over 99% of the fuel anyways, no matter what the length of the hydrocarbon is. And, being in the tank rather than in the fuel line, only a small percentage of the fuel actually touches the pellet. Besides, refineries use aluminium and silicon, along with heat and pressure, to break the hydrocarbons into the length they want, so any 'long' hydrocarbons in the gas are there for a reason.
Waste of money.