Ford C-Max EV+ mode
 

Why don't these cars STAY in EV+ mode? For about 1/4 mile around my house I get enough electric-only power to not need the gas engine at all (unless the battery gets too low), but anywhere else and you only get about 2/3-75% of the power it will put out in EV+ mode, which is just barely enough to get up to 45 MPH on level ground (As long as there's no one behind you - it takes a good solid minute)

I assume you have the regular c-max, not the energi. The regular c-max was never really designed to travel any real distance in EV only mode. Just like my Prius, it has an EV mode, but it really doesn't work all that great for whatever reason.

In a Prius, it's possible to get the full can of spam from the electric motor alone, but only if the battery is charged to 80% or higher--like after descending a long hill. I've only seen it happen twice, and only in the mountains.

If you don't have the Energi model, you simply don't have the battery power required to do any better. Your smaller battery not only means you can't drive very far on electric alone, but there's also a limit on the peak power it can output.

It sounds like you're trying to drive around using electric power as much as possible for maximum MPGs, which is actually not what you want to do in most situations. This video is for a Prius, but the concepts are the same. Usually, the best way to drive is like you're hypermiling a normal car, except you don't have to manually start and stop the engine when coasting or stopped. Electric power is used mostly for slow speed driving like parking lots and for helping to extend coasts/keep traffic happy. I generally accelerate kind of quick in my Prius in order to use the gas engine for what it's most efficient at, high loads. https://www.youtube.com/watch?v=3XxB6ma7qu8