THIS IS MORE INTENSE THAN MY TEST-DRIVE TO PALM BEACH: 46 hours and 9 minutes, my trip across the US in Audi’s new A6 TDI.

Our results were as follows:

Audi A6: 43.561 mpg; average speed: 65.4 mph; 14.63% over EPA rating

Audi A7: 42.653 mpg; average speed:65.1 mph; 12.25% over EPA

Audi Q5: 38.623 mpg; average speed: 64.9 mph; 24.59% over EPA.

Pretty impressive, and evidence — as I noted — that on long road trips, a diesel can do things a hybrid can’t.