All my diesels have looked bad when some one is tailgating with high beams. The particles really scatter light, and you are in the best position to see the scatter. The driver behind you may not even see the smoke. Seems like different fuels have a major effect. My Dad did not buy ag tractor diesel from his cousin because he felt that the (name brand) fuel smoked more and produced less power than fuel coming from Standard (now some British outfit). This is more of a problem for highway users because we don't buy 500 gallons at a time. My understanding is that all the majors can buy fuel from each other and sell under their own brand name. The fuel you buy this week at your favorite station may have nothing to do with the fuel you bought last week.