A minor point - acetone is a good solvent, but not quite as strong as it's made out to be here. It dissolves a lot of things well (paint, for example), but does a poor job with some oils and greases like silicone. I have several 1-liter bottles of acetone out in my lab right now; they are in the same Nalgene bottles (low-density polyethylene) they have been in for several years, and those bottles still look and feel quite healthy. It is very unlikely such a low concentration of acetone in gasoline would change the solubilizing characteristics of gasoline in any meaningful way.

Also, it is sold and stored in metal containers not because that's the only thing that will hold it, but more so because of the danger from static discharge when dispensing, i.e. you can ground metal.

Claims that this small amount of acetone would change the properties of gasoline so dramatically as to raise mileage 20-30% are just nonsense.

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2002 E320 4-Matic
2008 Subaru Outback
2009 Subaru Forester