I have two cars, one is a 1993 Nissan Pathfinder and the other is a 1995 E420. The pathfinder has 146k while the MB has 35K. I use premium gas for both. I recently saw a new product from Pennzoil that claims to clean fuel lines/system with one bottle poured into the gas tank when empty and then fill with gas and drive until gas tank is empty again. It also suggests using every 3000 miles (or every oil change). I bought a bottle and used it on the pathfinder... and Wow! The change was almost immediately and in less than a mile distance i noticed the pathfinder was not hesitating at take off like it used to do and now has better acceleration. I am tempted to use the same product on the Benz... any advice? Any harm with these products? I am not trying to promote the product here, just wanted some feedback Thanks.