A few weeks ago I was going from Philly to DC (in a rental Mazda 3, i am from WA). Saw a white X5 in left lane passing me. As it passed, I noticed the exhaust pipes and bumper were pretty black from soot. Falling for stereotype, I thought to myself "must be a diesel". Sped up to check the labels - 50i !.
P.S. Haven't seen a 35d with black pipes or soot in the back.