However I have to say that I'm a big fan of the Lucas Oil Fuel Treatment. I have a 2001 Acura that's rated at 29 mpg fuel economy highway, which is a fictitious number. In general duty with a long commute plus local driving I got maybe 22 or 23 miles per gallon for the first few years. But behold, at 90,000+ miles I started using this stuff and I get 27.5 miles per gallon on long trips now. It's quite the boost. I can't really tell if the engine runs smoother or I have more power because it's so subjective. But damn. This stuff pays for itself in fuel economy alone. Highly recommended, especially now what with the fuel costs approaching nearly a third of what Europeans pay!
Lucas Oil Fuel Treatment: The Official Fuel Additive of substitute!