[Matt Herring]

EV mode might work up to 47 mph but you won't be able to drive under 47 mph and expect to do it for 500 miles for a gas free trip. The Ford Fusion EV system works similar to the 2010 Prius where you can operate on battery under 47 mph but once your state of charge drops below a certain level (under 60% for the 2010 Prius) it is difficult to continue in EV mode while maintaining speed unless you are going downhill for miles and miles...especially when you need to apply some amount of throttle to maintain speed up hills. The same 20% throttle pressure that operated the car in EV mode at 80% SOC will trip the ICE at 40% SOC and any less pressure will not allow you to keep the car in the under 46 mph range and in EV mode.

And...once you have been using EV mode for a given distance and have depleted most of the hybrid battery there will be a battery safety feature that forces the ICE to run to recharge the battery.

While up to 47 mph mode is a very cool thing it is not a PHEV situation where a given distance can be done in EV before needing ICE/battery to operate the vehicle or having to plug-in for a recharge (see Chevy Volt's 40 mile range, any PHEV Prius conversion for 30-40 miles, etc).

In your example of the 500 mile trip you could do some very nice mpg's if you settle in behind a slower moving vehicle for great distances. While driving under 47 mph and using the battery only feature there might be some nice downhills that you can coast down with no pressure on the throttle to regen the battery. While this is a great situation to be in...you will still need to use some amount of ICE to propel the car up hills.

I just had this same situation happen to me driving from CT to NY. I was able to tail a slow moving RV for close to 75 miles and while my 2009 Prius can only operate in EV at less than 41 mpg I was still able to do alot of ICE pulse and glide (aka stealth P&G) at 45-50 mph behind the RV which generated some nice results. Had I been able to use EV at 47 mph and under the results would have been even higher. For that 190 trip my mpg was around 64 mpg thanks to tailing the EV for that great distance...and the other miles I was driving in the 55-58 mph range.