Review on Lucas Oil Fuel Treatment Quart - Tan Color, 1QT Size by James Fisher

That's my personal experience. It might work different in different type of cars. Using a leading brand 91 octane rating gasoline, I find no mileage increase on full tank adding a small bottle of this Lucas Fuel Treatment. Same result adding 2 or 3 small bottles of Lucas to the full tank of 91 gasoline. The mileage is identical weather I add just pure gasoline or add the specification amount of Lucas claiming to increase the mileage. I've tested it on 2 different car brands of the same class of the middle to full size sedans. No mileage increase ever for nearly 2 years testing adding Lucas to every full tank gasoline. On the other help, using this one regularly and adding twice the spec. amount of Lucas before regular smog check seems to help passing the test. It's not necessary like that. It might still fail the test but might pass on the second try using extra Lucas and driving your car a lot on highways between the tests. Also, a positive point here is Lucas doesn't seem to break anything so far at least. That's very important for a number of such called additives may harm the system they claimed to work for by a manufacturer. For this Lucas fuel treatment, I'm giving 1 star for Mileage increase. And, I'm giving 4 star overall for the fuel system maintenance and cleaning(though I could give 3 fine stars on a good side). For mileage increase, look for working fuel treatment. Or, it might work still for trucks, old-fashioned carburetor systems, etc. It might work still for Gasoline 87,89 and anything below Premium. I haven't tested such scenarios on a long run.