I ran 1/4 through my brake booster line, and 1/4 in the gas tank, and noticed a little difference. I didn't want to over do it since I had 95,000 miles. I ended up using the rest on my gf's mustang, through her brake booster line, and just a bit left for the gas tank. She had a bad idle, and after I ran this I changed the fuel filter, plugs, and air filter. Her car runs like it is brand new now and she has 130k on it. I'm thinking about using another half a bottle in mine, I've put almost 10k on it since, and I'll do it through a different line this time.