OK I've owned the thing for 2 years, but I never drive BEHIND it. Following my wife (no passengers), it was smoking a noticeable amount going up hills. And serious amounts of brown/grey smoke came out accelerating away from a construction slow-down. Not enough to hide James Bond, but enough to block the liscence plate. So what is normal?
We haven't had biodiesel in there for a month now (mea culpa). And it isn't particularly cold out, that brownish stuff didn't look anything like it was condensing in the cold. I ran injection cleaner through there went we ran out of the BioD as a precaution, but could it be dirty injectors? Also, changed air filter 3k ago. We're due for an oil change, we're at 18k on it. Wife drained the battery recently

(it took back the charge) but the wife said that "it does that alot, even before THE INCIDENT". Also, could it be that I'm used to the lower particulates/sulfer etc from 100% ASTM BioD and this is what you get with dirty diesel?
I kinda like it, actually, as long as it's normal. Drop a muffler and add some straight pipes = muy macho!