So, what's more efficient - a diesel or a hybrid? The German magazine Auto Bild drove the Mercedes ML 320 diesel and the Lexus RX400h from New York to San Francisco to find out which one was the master of mileage. The results from this cross-country trip give the edge to the diesel, which should come as little surprise for what we assume was mostly steady-state highway driving. The Mercedes' average of 37 MPG edges out the Lexus' 33 MPG and impresses the hell out of me in the process (note that the link below states the mileage using Imperial gallons). Also noted is that the hybrid was marginally (about 2%) better in urban-type driving. Which would I pick, you ask? Based on this, I'd probably go with the diesel, but I do very little true stop-and-go type driving. I'd also prefer said diesel in a nice midsize wagon instead of a "soft-roader", but that's a different discussion altogether.