Ford offers a less efficient, naturally aspirated engine in the Transit Connect. Turbochargers make engines more efficient, but if a turbocharger goes south that more than wipes out all the fuel cost savings. Turbocharged engines also need premium gas. A lot of commercial and government fleets have their own gas pump (which dispenses regular gas), so they don't want to add any turbocharged vehicles to their fleets. Those new Mercedes-Benz postal vans need 91 AKI gasoline. So, maybe USPS will accept the added cost of 91 AKI for better fuel economy.