I have a 97 z28 with 62k miles. Last week I did around 3/4 can through the vac line and the rest of that bottle in the oil. Dumped the other can in the fuel tank and also did the Deep Creep. Everything worked as it should and the car has been running better since. I still have'nt gone through the whole tank of gas about half tank now. The only thing is in the morning, cold starts are a little rough. Please don't tell me by chance the opti went out right at the same time. Oh, almost forgot, I changed the oil about 60 or so miles (per the main guy at Seafoam) after adding Seafoam to it. Used what I always do...Mobil1. I am due for changing my plugs...I have over 20k miles on NGK TR-55s. Could that be the only problem? The guy at Seafoam said it won't mess up the plugs and could possibly even clean them. What do you think?

 

I think you should change the plugs and see what that does for you.

 

Yeah, I hear ya. I've just been dreading it. Should go easier second time though.