Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Works like it says.

Used it on my 10 yr old BMW. My gas mileage of 19 mpg improved by about 1-2 mpg in town and 1+ mpg on hwy now back to 29 mpg. {I use 93 octane}. Performance is better though; it has its old spunk back. When you hit the gas pedal, it moves like it was 2 years old again. I liked it enough to get 3 more to put in the other cars for the family. This one works for us. It may not meet expectations of increasing mpg 10-15% like some claim, but did improve performance and added some mpg.