A colleague (not a Prius owner, but interested in alternative fuel vehicles) asked me if I knew anything about the claims being made by a company that sells an additive called Ethos (I think it's basically acetone). The claim is that mileage can be improved by up to 20% or so simply by adding 1 oz. per gallon of the stuff. Read about it here:
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My brief bit of research suggests that acetone may have some positive effect on gas efficiency, but my gut tells me otherwise, especially considering the hard sell. I have no interest in it for myself (a Prius owner), but I told him I would ask the Prius community, since they tend to be well-informed in these matters. Any opinions or facts to share? Thanks, Doug