I was wondering what the best fuel injector cleaner was and so I posted in on another board...and one person came back saying he's heard to use these products only when changing the oil as it "mucks it up". True? Will fuel injector products ruin/poison/or otherwise contaminate a motor oil or was this person thinking "oil additives"??? Anyways, any opionions on the best fuel injector cleaner? Or are they all the same? ie. is the $3 bottle the same as the $15?? Any to stay away from ie. aren't safe?