Smile! I must admit that I have used this same ploy repeatedly from
California to Canada. I just point to registration and the plaque on the rear
hatch that says diesel and insist it is physically impossible to have been
doing 80 in a 65 mph zone. There is always a short but awkward pause as
conflicting neurons  attempt to grasp the concept of measurement vs. obvious
wisdom (Vanagon Diesel Camper - top speed 60 mph with aggressive tail wind).
Then, still fraught with uncertainty, I'm told to drive carefully and to
watch my speed.

I then fire up my 1.8 l 8 V chipped Digifant engine and motor away. Once
(Oregon, I believe), I showed him the engine. He noticed how small it was and
remarked that it looked just like a gasoline engine!

BTW, I always keep a small container with a diesel soaked rag in the rear top
stash area and take it out if ever I'm inspected. Good aromas!

Frank Grunthaner