I have a 2002 ML320 with 85Kmiles thats shaking especially when the gas is less than a half tank. My wife drives the car 90% of the time and admitted to using Regular gas in it. I believe that is the cause of the issue but thats just my speculation. I took it to get service at an independent repair shop, changed the oil, spark plugs and had the wires and coils check. The mechanic says he didn't find any issue but the vehicle still shakes. I'm thinking about trying one of those gas treatment. Is that recommended or any suggestions would be appreciated? Thanks