What I'm talking about is fully shutting the engine off, in order to maintain speed down gentler hills.

 

Why on earth would you do that?

 

Because the weight of the car allows it to maintain speed. see here

 

What you're advocating is illegal in all 50 States and Canada. Why? Because quite simply, it is unsafe.

When you suddenly need a burst of power (or power steering or power assist brakes) to avoid an accident and you find yourself crunching into a truck or something that unexpectedly pulled out in front of you while you were free-wheeling down a hill with the engine switched off, don't say we didn't warn you.

 

I am aware.
I hug the right lane, I always pay attention to the lanes in front of me, my maximum speed never reaches anything higher than 60, I cover the brake pedal the entire time, and the brake booster holds enough vacuum with the engine switched off to fully stop the car on a 7% grade at 60mph without losing power assist. Also (at freeway speed) power steering really isn't that crucial for me.
It is dangerous, but not much more than using a cell phone, speeding, having a prolonged conversation with passengers, etc.
I will continue to be careful.

 

Do you believe everything you read on the internet? That effective achieves zilch. Beyond being dangerous, fuel injected engines are efficient enough that doing that does nothing to increase MPG, if not costing more becuase of constant restarts. Perhaps in a Prius, as the example uses, when the engine is on electrical power anyway it works, but not with a straight internal combustion engine.

And I was getting 28 on the interstate with a 2005 V6

 

When I can travel a mile, two miles, three miles (I believe my current record is 3.6) without using any gasoline, I would offer that it would increase the number of miles I would get per gallon, simply by virtue of the engine not using any. You roll further with the engine off than under injector shutoff at the very least. I'm not saying it's the safest method of freeway driving, but it doesn't really matter to me, I save a bit of money.
Here's my mileage log

 

You are not safe. Some would say not too smart.
How about just losing 25 lbs of body weight, ditch the back seat and spare tire? Probably be the same result. only safer.
Plus if you lose 25 lbs, you spend less on food, therefore saving money over course of your life. not just while driving.

 

|I see your point there Mystic

 

I am 6' and 130lbs (vegan). If I lost 25lbs I would most likely die. I already ditched the spare tire, along with a few other parts of the car that I don't use (windshield washer reservoir, carpeting in the back, A/C, etc). That being said, I understand where you're coming from. I understand the risks involved, and I am willing to take responsibility for whatever the consequences of my driving style are.