Average mpg is what you want it to be. If you reset the average every time you fill the tank, it's a tank average. Tank mpg and short trip mpg work together to show what you're doing now and how it affects the tank.

 

This just means that if you're racing, you keep the engine in the 4K+ range to get you the most power. It does not mean the engine is getting good mileage in that range. To keep your car moving at a consistent speed at 45ish MPH, you need something like 2-5 hp to keep that speed depending on car shape, weight, wind speed, etc. Which your engine would give you in about 8th gear at 1.2K rpm... like you said here:

being in 6th and going at a consistent speed at 37 is how you maximize fuel economy. Trying to accelerate in 6th from 37 though, is a bad idea. Accelerate closer to the power band, coast/maintain constant speed in the highest gear you can manage.



This is because in 6th gear going downhill with no throttle, the fuel injectors shut off and you burn no gas, despite the engine turning because the wheels are pushing the engine. If you're in neutral, you're burning about 0.2gal/hr or something to keep the engine spinning. It's minor, but if the hill is steep enough that you can maintain speed or barely have to blip the throttle, staying in gear is better.

(Hypermiling would be to shift to neutral while turning the engine off, so you don't have the extra resistance from being in gear but you're also not burning gas to keep the engine idling. Most people view this as excessively dangerous and not worth the fuel savings, which I agree with, but it's not the point of this reply, so i don't propose it as an option 3 above.)

The shifting dummy lights are kinda dumb, but some of what they do is actually correct. If you accelerate at less than 2K rpm, it goes blue to tell you that you'll get better mileage by downshifting to accelerate. If you utilize engine braking, they turn green. If you're going 35 in 2nd, they'll be blue to tell you to shift. If you coast in neutral, they turn blue because you'd get better fuel economy in 6th. When you're stopped, they're blue because you're getting 0 MPG.

It all comes down to knowing why you're doing what you're doing.

 

Thanks for the hints and tips. I do appreciate them as I learn. It has taken me a couple of days to think about your comments.

I am interpreting this as it is better to be in gear if your car is on a flat stretch, or on a decline and you do not want to accelerate due to gravity. If your car is on a steep decline and will accelerate you will increase fuel economy by coasting. Coasting uses gas as the car is in idle, but will allow you to accelerate on a decline, burning up idle gas but naturally increasing forward momentum, saving more than the idle gas. Being in gear but off the gas will not use gas (DFCO) but will not let you accelerate due to a decline.

If (on flat or slight decline) or (on a steep decline and you do not want to accelerate)
---stay in gear, DFCO will save you idle gas;
elseif (on a decline that will accelerate car above current speed)
---coast. You will waste idle gas but increase forward momentum;
endif

I guess it really does depend on your situation. Every little bit helps though, so I'm paying attention to these little details.

 

Coasting in gear is engine braking. If braking is appropriate, that's the way to go. If braking is not appropriate, the bit you burn idling is still better than braking.

Idling at 60 mph, my Fit gets around 270 mpg. I could make that number look higher by engine braking, but it's just a stunt that would make me burn more gas over the whole trip. Braking in any form is best avoided whenever possible.