Is there a benefit to coasting?

To put it simply, all gasoline engines use gas while running. When accelerating they use even more. When coasting they use less.
Hybrids still have gas engines but: 1) when accelerating the use electrical power to assist which is more efficient 2) when coasting and braking at speeds under 40mph (on many models) the gas engine will shut off and use no gas.

For example: Here are my real world numbers from my 2006 4wdi Highlander Hybrid SUV (EPA sticker 30 City 26 Highway) 20mpg City when accelerating to 30 mph and then braking to 0mph when I got to the stop sign or street light over short distances. 32mpg City when cruising down the avenue with some acceleration to 40mph and some coasting down to 30 mph and infrequent stops. 28mpg Highway if I kept it under 60mph. At 80 it would drop to about 22mpg.

So in a nutshell, all cars get better gas mileage when coasting but hybrids do it best because of the ability to shut the engine off automatically.

For more information search for the "Pulse and Glide" technique.

 

If I put the wife's 2011 in N when coasting it does not slow down near as much as when I simply lift off the gas.

 

The dealer was likely referring to coasting in neutral which will turn off regen brakes. And pulse and glide uses light pressure on the gas pedal to find an energy free glide while still in drive. So regen is still right there when you brake.

 

Isn't the mileage good enough without worrying about any of that? I've decided I'm just going to drive normal and live with the 50 plus mph in the warm weather and we're getting about 46 mph when it gets really cold out. The drop in mileage bugs my wife, but I'm really not going to complain about only getting 46 mph.

 

In a word... Yes. Whatever floats your boat. Some people like to play the ultimate mileage game and in that game, the sky is the limit and no technique is too bothersome to attempt. For others, the mileage they get from normal driving is sufficient. For my part, I'm just light on the pedal and avoid jackrabbit starts, and then let the CVT do the rest. I drive all my cars that way except for my S2000. Pulse and glide with that car would be blasphemy.

 

I would attempt to discourage you from using N whenever possible.
Since the Prius has no clutch that operates, the gears are always engaged. N works by not passing any power into or out of the Motor Generators. No Regeneration can take place in N, the engine cannot be started in N, it may not be possible to stop the engine in N.
You can destroy M/G1 if you gain speed in N, as the engine can't automatically start at 41 MPH* as it should.
You can drain the HV Battery in N as you can't generate any electricity in N, some car washes want you in N. My advice is to find some other car wash.
N gets worse gas mileage than D when coasting to a stop, as under 41 MPH the engine can stop in D.

* this speed varies slightly in Gen1 and 2, and is closer to 62 MPH in new Prius.

So why have a N? The US government requires an N. In case of Unintended Acceleration, you want to shift to N and destroy the drivetrain^ rather than imperil your passengers.

^The lack of damage to the drivetrain makes me suspicious of all UA cases with a Prius. When a Ford Aerostar I was a passenger in suffered UA, the driver slammed it in P hard enough to damage the drivetrain.

 

Lifting your foot off the gas puts the car into light regenerative braking, just enough to sort-of simulate the engine compression braking of a 'normal' car in the same situation. This makes it more drivable to people accustomed to traditional cars.

Applying a light pressure to the gas pedal can get rid of this synthetic drag, producing the same efficiency as 'N' without the risks.

 

In my c, the point where the ICE is forced on is between 76 and 77 km/h indicated - this would be between 47 and 48 mph.

I would also advise against using N. Gliding with the pedal is a better way to go, not to mention that it allows you far more freedom to have a less strict attitude towards pulse and glide (ie. accept P&G as a proven ideal and use it as a guide to influence your real-world driving rather than follow it as a dogmatic rule with no margin for tolerance of situations around you).

The beauty of the c is that the ECO Score display does a reasonably good job of training people to get half-decent mileage without really thinking about it. Beyond that it just depends how far you want to go with it.

 

46 MPH in a Gen3 Liftback, non-PiP.

I can't speak for the 'v' (probably lower speed), 'c', or PiP.

 

Sure. That's the beauty of the Prius. You can drive it without a care and get great fuel economy or you can play with different techniques and get ridiculously good fuel economy.

Mine

 

GenIII but the same principles apply.

 

I actually don't look at the numerical score any more. The initial press suggested it was a rating based on your last 100 drives, but I do not believe this to be correct.

I do look at the rating out of 5 for start/cruise/stop and of course the HSI (the bar graph) is everything. The video F8L posted above explains how to understand the HSI. Despite the slightly different apperance in the c, the principles are the same.

The post by maciek here is also a good intro: New to Prius C: things to watch out for? | PriusChat

 

Driving a Jeep for the last two years, and it being geared for off-road, I've been gliding for a long time. Pretty easy to do, just let it glide!!