From 46mpg to 52 easily, thanks priuschat!

I have to concur, when I first got the Prius, about 5 weeks abo, I just "drove" it and averaged 52 on the CONS, not bad but not what others reported here. there is a thread about "getting the hang of it". I followed that and my CONS mpg jumped from 52 to 57. if the traffic permits, or lack there of, I slowly accelerate with the HSI meter just to the right of the ECO sign. if I'm in traffic, I will accelerate with the meter just getting into the power side, then as I approach the speed limit I'll back off to the right edge of the ECO symbol, achieve the speed limit and then pulse and glide.

 

Yes, the HSI actually WILL educate us on how to drive for economy, if we pay attention.
I find my MPG has improved on ALL my cars as a result of this education process...

 

I run just to the edge of the ECO symbol and my average has improved as well. However, I seldom "accelerate", I'm usually losing speed and settling out around 53-55 mph if left to its own devices. Are you running 10% ethanol in your fuel?

 

Great input. This has been my experience too. I'm getting much better total gas mileage, and have had up to 78mpg on my 20 mile commute, which is pretty conducive to good numbers.

With this approach, my driving pretty much hangs around 3 places on the HSI: 1) Just below the power area for accelerating from a standstill; 2) Just below the right edge of the ECO sign; and 3) Gliding. Simple.

Here's a more complete writeup that I did a few weeks back:

Starting
- I Pulse/accelerate with the HSI just below the power area. (This isn't the exact sweet spot for the engine, but it's pretty close and gets me up to speed in a reasonable time.)

Non-Highway Driving
- Once I get up to speed, i do pulse and glide. Pulse is done at a level on the HSI just under the right side of the ECO symbol. (This is the sweet spot of the motor at 15kw or 20HP.)
- Where road conditions allow, I only pulse to 44mph so that the motor doesn't start to spin and create a 5kw drag. (it really is amazing how far the Prius will glide at 44 mph compared to 46 mph). To stay under 46mph I sometimes even find the need to glide up a hill for a short time to bleed off a few mph.
- Of course I also do a little anticipatory driving on hills where I accelerate on a downhill or on a flat area leading to a hill, and then bleed off some speed on the uphill. (Unless I'm careful I tend to slowly accelerate up hills, with the speedometer incrementing another mph every 5 seconds or so. If I'm already at a reasonable speed I have to intentionally back off the throttle a bit to keep speed constant instead.)

Highway Driving
- Similar to non-highway mode, I try to pulse or maintain speed with the HSI at just under the right side of the ECO symbol. On the highway, during low load conditions, my challenge is to not let the HSI drift down to just above the centerline, where the efficiency of the motor starts to drop off dramatically. (This is still a bit strange to me, since the links in this thread mention that efficiency is lower at this HSI reading. However, the instantaneous mpg display shows as quite high...) In those low load conditions, I don't hang around the centerline anymore, but I glide instead.
- I try not to exceed 65mph since the air resistance begins to get much higher and I can't maintain speed at the pulse level described above.
- Of course anticipatory driving on hills applies here too.

Misc
- I rarely run on battery power anymore. This is a key piece of advice from experts on the forum. This too was counterintuitive to me, because I could see my average mpg going up whenever I ran on battery-only power. However, what I couldn't see later on was the cost and inefficiency of making up that battery state of charge with the engine.

 

snip...

There's a lot of wisdom in that statement.

 

I like to use cruise control to maintain steady speeds - how do you think that would impact mileage?

 

Seems like it would be fine on fairly flat terrain. At non-highway speeds, though, you'd be able to do better with pulse & glide. On large hills, the attempt by the car to maintain speed on a sharp incline would burn a lot of fuel. For example, on the mountainous interstates in eastern TN, cruise control is really suboptimal.

 

Are you driving in normal, eco, or pwr mode? I normally drive in eco and want to have a proper reference for the "right edge of the ECO sign."

Thanks.

 

Yes I normally drive in ECO, though I've read on this forum that results are similar in other modes too since the primary difference between modes is gas pedal sensitivity

The ECO symbol I mentioned is the one located on the HSI just above the centerline. The right edge ends up being about 1/4" to the right of the centerline. On other posts I think I've seen that in this spot the mpg approximatel tracks mph (very rough ballpark)

 

Just keep in mind that different people have different opinions on the best spot for accelerating; the best thing would be for you to try a variety of different ranges yourself, and see what gives you the best fuel economy. dcscm1 likes to accelerate fairly slowly it seems (just right of the ECO light), I accelerate fairly moderately (typically just short of filling the Hybrid bar - eg just before filling the PWR bar), and (if I recall correctly) Bob Wilson accelerates a bit more briskly (filling a good portion of the PWR bar - but keep in mind that when you first fill it all the way, the engine is still nowhere near its maximum output).

So try a few different things, maybe a tank at a time, and see what gives the best balance of fuel economy, rate of acceleration, and not obstructing traffic. In general, the Prius will probably do fairly well in quite a wide range of power output, so any of these may be acceptable.

 

To clarify on how the driving mode impacts the car, does it only adjust the pedal throttle mapping? Does the HSI get shifted or anything too? My best tank was about 53 mpg, which I'm happy with. But typically I'm closer to 49-50 mpg. I'd like to try to consistently keep it above 50 mpg.

 

Is running 10% ethanol any better? How long you been doing it?

 

Also tries to run the A/C a bit more efficiently.

 

Just to add my understanding is that this works because each of them is very efficient:
1) Close to peak torque - good bang for the bang, as it were
2) Engine running very efficiently at steady state. I believe it typically returns mpg about 1.5 * mph
3) No power draw, no engine braking.

Note to others that with this approach the car will always be varying speed but doing so very efficiently.

 

You get that kind of mileage improvement when it simply gets warmer outside. LOL.

 

Macman, I absolutely agree. Different folks have various approaches to where on the HSI to accelerate at.

For the record, I accelerate from a standstill similar to Bob Wilson, with the HSI almost at the PWR region (and sometimes into it if I need to get going more quickly). I also accelerate like that if I have to increase speed by a substantial margin (over 15mph or so).

I use the Edge of ECO for two things:

1. Steady state cruising where pulse and glide doesn't seem to fit well. (e.g., driving up a slight incline, or maintaining speed on the highway).

2. To do micro-pulses during Pulse and Glide in traffic. With Atlanta traffic, my max and min speeds in P&G can only be 5 to 7 mph, or else other drivers get apoplectic. Also, traffic/hills/lights mean that I'm rarely able to glide for long periods of time. So I do a micro P&G. At the Edge of ECO, my pulses tend to be around 4 seconds or so.

 

Great point INATM. Yes, this results in varying speed. Some of the variation is due to classic pulse and glide, but the other variation is because (2) is a "constant power output" where speed can vary by terrain.

I began experimenting with (2) based on the excellent articles by Hobbit that are linked about halfway down this thread, where he says, "it's not just about steady-state sustained speeds -- it's about holding a constant optimal power output when needed through a variety of conditions."

This may not be the perfect approach, but it's provided me with much better FE numbers than I've ever had. Plus, it's simple enough that I can do 1/2/3 almost on mental auto-pilot now.