Actually, the Techron additive does work. The concentration is gas is small, but I run a bottle of the stuff every 5K miles or so. I like Diamond Shamrock (Valero) the most. I believe they are out of San Antonio, Texas so I don't know how far north you will find them, but I consistently get good mileage and their price is usually lowest. Shell is terrible, and Exxon is hit or miss. There is one Exxon that makes my mom's Taurus always ping. BP is great, but the only station even close is at least 5 miles away.
