Constant low speed vs. always green light

[Atlantix]

I am approaching 5K miles on my 2010 Insight - actually I should say OUR Insight... working opposite shifts we both drive the same car to work. So I pull gas mileage up, wife pulls it down. But that's another story, and it's partly due to different driving conditions.

Until now I was under the impression that driving around 55-60 MPH on the interstate gives me the best mileage; this morning, after some reading on this forum, I tried something different. I pushed it all the way until the light turned blue, then backed off a little to keep it green. So I found myself a couple of times going 80 MPH and still on green (my commute is on I85 going north and we have plenty of hills and valleys over here).

To my pleasant surprise, my gas mileage stayed pretty much the same! Will do more testing on the way home - which increases my daily gas mileage as I'm driving overall hill up in the morning and hill down in the afternoon).

So what's going on here? Is it more important to keep it on green than to drive at percieved economical speeds? Those of you with cruise control, what is your experience driving on cruise vs. keeping it green at various speeds?

[For the record, my best day so far was 55.5 MPG on my daily round trip, driving 55-60 MPH].

Thank you,

[buglermcd]

Unless you're drafting, you'll get better mileage doing 55-60, as long as you're at a constant speed. There's a ton on wind resistance to push against at 80mph.

Now, if you can find a route to work that has minimal stops and a top speed of 50, you'll watch your fuel economy shoot up.

[Atlantix]

I reset my B counter every morning when leaving the house (I left A on "lifetime").

Normally, by the time I get to work, my gas mileage is about 51 or 52. My commute is about 24 miles one way, of which 16 miles on I85, and I have around 15 red lights on the side roads, no green wave. When arriving home, my overall gas mileage is 53-55, increasing somewhat on the way home (driving more down hill).

This morning I did 51 on the way in, driving as described above, as opposed to "snail mode" before...

No drafting here; tried it for fun, it's not safe, it's not for me, even at 50 feet behind. I prefer staying alive...

[Cobb]

Think of the blue/green indicator as a load indicator. The best indicator of your driving vs fuel economy is to set the screen to see that bar that moves across the bottom and shows your average mpg for that trip. Then drive to keep that bar at the highest reading. Next best I do is to use little assist as possible, but regen frequently.

I dont doubt that you can do 80 in the green if its a down grade or the area is buffered from wind, but you are likely using gas vs electric to maintain as the hybrid system in my experience slacks off above 70.

As noted, unless drafting, my best fuel economy comes from going 55mph or less with no ac. Going 36mph down back roads in rural VA I freqently see 74mpg with no ac.

[TdG]

Atlantix, that was one of my doubts about the Insight.
Normally I cruise arround 60 to 65 mph (metrically that around 100 km/H por you ) but sometimes when I speed up a beat (say to 80 mph) I can still get a green dashboard, but instead of making 59 mpg (around 4L/100 Km) now I am doing close to 30 or 40 mpg.

I believe that the Econ and Mpg panel of the HUD dont speak the same language

I had already trued to discover how low can the gas consumption of the Insight go (without using de IMA) and seen to me that with the certain conditions you can have very decent value between the 55 and 60 mph.

That one time I was cruising at 72 mph and the mpg-display was showing the amazing mark of 78 mpg. Sadly I couldn't reproduce the achivement so far.

Take Care.
TdG - from Portugal to the World

[Atlantix]

Seems like you guys are right - I tried to duplicate the "performance" but failed.

So I don't know what happened that morning... tail wind or instrument malfunction?

[Cobb]

One reason it seems to take me forever to post mpg claims. I do it twice to repeat it incase its a fluke, tail wind, etc.

Lets try driving with the instant mpg readout and bar tha tmoves across the bottom of the screen. Keep this at max.

[buglermcd]

Originally Posted by TdG

I believe that the Econ and Mpg panel of the HUD dont speak the same language

They don't. The MID shows actual mileage based on calculation of speed vs. fuel being pumped into the engine by the fuel injector.

The ECO assist colors are purely based on speed and throttle. It's a relative meter. It judges you by telling you how eco-friendly you are for that speed, in those conditions.

You can be green at any speed. You can also be Blue at any speed. It's all a feedback system for your driving style, at that moment.

So, say you are going 65mph and are in the green. That means you are driving at the most fuel efficient way, for THAT speed. But then you hit a hill. Well, to maintain that speed you need more throttle. The Eco Assist turns blue. You're still going the same speed, but since the conditions have changed (the addition of the hill), you no longer meet the requirments to stay in the "green" zone for that particular speed.

Same thing when you slow down. For the entire time you apply the brakes, your engine is off, and not consuming gas. But if you brake too hard, your Eco Assist will turn blue. That's because you are not slowing down at the optimal rate for the car. If you slow down slower, you can regain more energy through regenerative braking, but not if you quickly drop speed.

So in review; do not follow the Eco Assist for your only measurement of Fuel economy. It's simply a tool to help you change your accelerating/deccelerating behaviors. Once you cruise, it doesn't help you much.

Use the instant Fuel Economy page on the MID to find the best speed for the fuel economy you wish to have.

[Atlantix]

Thank you guys, much appreciated advice for the novice!