I've been using Shell fuels almost exclusively for multiple years now because it's Top Tier certified, everywhere in my area, and I use their Fuel Rewards program. I've heard from various sources that using the same brand of gasoline (and presumably the same additives) can cause build-up over time. I understand that all gasoline as delivered to gas stations is more or less the same no matter where you go; but over time, is there any truth to alternating between different fuel brands as some stations may have additives that clean certain issues that one may not? (e.g. Shell's proprietary additives versus Exxon's?)