Amazon.com customer reviews of zMax engine treatment are extremely positive as of 2015, with many claiming that the product works very well. Customers gave the zMax engine treatment oil and the zMax engine treatment kit an almost perfect rating, claiming the products increased gas mileage and improved performance.
AutoZone customers also gave zMax engine treatment an almost perfect rating and claim that the product works, and most recommend the product. Advanced Auto Parts customers also claim the product works well, and the majority of reviews are positive; 91 percent of respondents claim they would recommend zMax to a friend. Negative reviews typically relate to the price or marketing of the product, although a few customers are dissatisfied with the performance.