He was using neutra he got with me on my last order,
01 Ford Taurus 25k mi. He ran 12oz.when he got it,and got better gas milage,6oz. in the second tank of fuel,his last fill up no neutra was added, the check engine light came on and car idles kind of rough,he usually uses mobile,exxon or citgo gas.I was thinking it might be the fuel since it didn't happen until his last fill up without the neutra.