Hi guys,

I got a 5 dollars off coupon for Pro Gard Fuel injector cleaner from chevron from costco, so I bought a case back home. My question is how does the fuel injector cleaner works? I know that there are many kinds of injector cleaners (from cheap one to very expensive one); how they are different from another. Please tell me more!

I sometimes feed my car with shell 91 gasoline and sometimes I feed my car with 87. Please give me any suggestion!

Thank you!