Base V6 engines have had 10% of the half ton market for about 20 years since the demise of Ford's 300 inline 6. In the 15 years I owned and followed the half ton market, there was an immeasurable difference in fuel consumption for the same driver for the same conditions between the base engine and the mainstream V8 (or the 3.5L Ecoboost lately). Same goes for axle ratio, tallest to shortest. People that leased trucks or otherwise bought 2-3 of the same generation truck used within 10% of the same amount of fuel. Do you know what they all comment on? Driveability/power when they want it. They don't want to wait 2 seconds for the trans to shift to a lower gear. They don't want to wait another 1-2 seconds to actually shift 1-3 gears. That's a primary reason why the Ecoboost and the Ecodiesel are desirable. You want to go? You are already in the sweet spot for engine torque. Half a second for turbo to spool.
Ford expected the EB to have a bout 30% take rate prior to launch for 2011 model year. Actual take rate was closer to 40% immediately and now even higher. The 70% expectation may come from the 2015 2.7L EB introduction. Has anyone followed other vehicle types? Mid sized sedans 1980's 85% V6. Today, 98% 4-cyl. Ford doesn't even offer a V6 in the Fusion. Same with Escape. Maybe the half ton truck market will be next?