Instruct: Classify the given Amazon review as either positive or negative.
Query: Not suitable for Chevy Blazers

I put 6 of these into two different Blazers. A 1999 and a 2001, both with the Trailblazer trim package. After 6 months of use, both engines have seen a significant decrease in fuel efficiency, losing an average of 3mpg. That's a 15% drop in fuel economy. I've since learned these plugs do not do well in GM engines in general and Chevys in particular. I will be replacing them all this weekend with stock platinum AC Delco plugs.Do yourself a favor. If you are considering these plugs, do a little research first and make sure you are going to get out of them what you hope. I didn't and now I'm paying for it.I am not saying these are inherently bad plugs. It's just that these plugs don't perform well in my application.