Depends. If there's so much soot it reduces time between engine overhauls, that might not be good. Then again, TEL causes shorter overhauls as well, so... Any

Depends. If there's so much soot it reduces time between engine overhauls, that might not be good. Then again, TEL causes shorter overhauls as well, so... Anyway, like I said, there's a boatload of other properties the fuel has to satisfy as well. If it were as simple as just switching to p-xylene, presumably they would have already gone down that route.