Long Trip MPG

Same car (even same color), pretty much the same results. Next trip I plan to put it into Power mode before setting the cruise control - I think it may provide better results on hills. (and 45mpg is still a lot better than the 24mpg I used to get in a similar-sized car)

 

Thats sounds right. I would think if you drove 65 on cruse you would be able to get above 50mpg without trying. In the summer my car would get 55mpg going 65mph.

 

I too would suggest trying to cap your MPH at 65 MPH. Bob Wilson has posted some great reading about the variations in small speed differences.

You may wish to do a search in the group/forums.

But try reducing it to 65MPH and I think you will easily top 50MPG!

 

There is 60 mpg at 60 mph rule in a good condition.

Ken@Japan

 

The 60mph rule really work.
My last car was a Matrix stick shift, and by putting it in neutral on downhill and keeping it at 60mph I could do up to 45mpg. Now the only drawback the speed limit is 65 and most of the users do 75, still I kept to the right lane but I am sure did upset a few.
The good thing is that the pri does it for me now, and my first tank was already better than my best matrix tank without doing anything special.

 

When I drive to Fl. I limit my speed to 65 mph max. Gas mileage difference is at least 2-3 mpg on the trip. The only difference is in 70 mph zones I limit my speed to 65 mph. In the 65 zones I will drop down to 61.2 or 100 KPH when I can. 29 mpg limiting my speed to 65 mph vs 26.5-27 mpg running the speed limits in my Volvo 960.

1170 miles and the difference is about 45 minutes longer.

Once you go over 65 mph you gas mileage will dump quickly.
I have found over the years most cars sweet spot is in the 60-65 mph range. Meaning the best fuel mileage VS time spent driving on a long trip is achieved.

 

The Prius 2010 has been tested in Italy by "Quattroruote" car magazine (one of the most authoritative out there in Italy, if not in Europe) and, as for all cars, they tested the constant speed (instantaneous) fuel consumption of the Prius with the following results (the numbers are not coming from the Prius MFD, they use their own, pretty high tech and highly accurate, instrumentation):

90km/h (56mph) 26,8km/L (63.04 mpg)
100km/h (62mph) 23,4km/L (55.04 mpg)
130km/h (80mph) 15,4km/L (36.22 mpg)
(this is the italian highway speed limit and the advised speed limit for germany)
150km/h (93mph) 11,7km/L (27.52 mpg)

This is also what they got in their tests of:
city 29,4km/L (69.15mpg)
regional/suburban roads 21,3km/L (50.1mpg)
highway (130km/h) 13,7km/L (32.22mpg)

BTW: they also test braking efficiency by checking the length required to go from 100km/h (62mph) to 0km/h-mph for 10 times in a row - it needed consistently around 46m/151ft to get to a stop.
Though this has been rated as "good" (around 30m/98ft is rated "excellent", above 50m/164ft starts to be "bad"), they claim this to be "the price to pay" when driving with 15" narrow cross section, low friction rolling (for improved MPGs) tires. Though on the other hand, *absolutely* no fading/performance deterioration of the braking system was noticed (considered on the contrary really good).

 

Thanks!

Bob Wilson

 

As you can see by Bob's graph, there is no sweet spot. The faster you go, the more fuel you burn, simple physics

 

I thought I clarified it in my post.

You can drive 1000 miles at 56 mph getting 63 mpg, or you can drive 62 mph getting 55 mpg, or you can drive 80 mph getting 36 mpg

1,000 miles (56 mph) with stops averaging 51 mph would take you 19.60 hours.
1,000 miles (62 mph) with stops averaging 57 mph would take you 17.50 hours.
1,000 miles (80 mph) with stops averaging 75 mph would take you 13.30 hours.

15.90 gallons vs 18.2 gallons vs 27.8 gallons

During that 1,000 mile trip (56 vs 62 mph) would I spend an additional $6.20 on 2.30 gallons of gas to get to my destination two hours and six minutes earlier. Probably

Would I spend $25.90 more (62 vs 80 mph) on 9.60 gallons of gas
to get to my destination four hours and 12 minutes sooner. No way.

On the other hand if I'm driving less than 100 miles would the difference in time be worth the additional fuel usage driving above 55 mph. No

 

Sorry to burst you bubble but many Italian Prius owners complain that the consumption data provided by Quattroruote at highway speeds are far from being correct. Many users infact report a consumption of 5,2- 5.4 l /100 km (about 43 mpg) at 130 km/h (80 mph).

I am going to ask to some guys from Hybrid Synergy Forum (Italian community about hybrid vehicles) to chime in and comment those figures as they are certainly more knowledgeable than me on this matter. IIRC the very founder of the site (aka The Tramp) has driven the Prius at max speed on the German autobahn and was unable to replicate such a bad highway consumption at 80 mph.

Edit: since it's 2.30 AM here, it might take some time for them to chime in.

 

Have I been summoned?

Here is my thread regarding the top speed spree in Germany: http://priuschat.com/forums/gen-ii-prius-fuel-economy/47370-top-speed-mileage.html

Yes, Quattroruote may be the best selling car magazine in Italy, but it has many times proven to be biased, with favours leading towards German car markers.

The Prius 2 was tested by quattroruote giving 42 MPG city, 40 MPG country, 24 MPG motorway....

Obvoiusly many other Press took this info and spread the news that the Prius is useless in motorway driving.

Quattroruote also compared VW Direct Injection petrol (TSI), Peugeot Turbodiesel and the Prius in a loop around Milan: The diesel won with 33 MPG, Prius second with 31 MPG, Golf with29 MPG.
We did exactly the same route (it was published) with two cars on a very windy day and got 51 MPG on one car and 55 MPG on the other car.
The story is here: Quattroruote questa volta l’ha fatta grossa… | Alla Guida

With the prius 3, OTOH, they achieved too-good-to-be-true mileage in city driving, they still overshot with motorway mileage. People in Italy driving at 136 km/h (85 mph) indicated on the GPS declare a OBD mileage of 48 MPG - far from what declared.

Even quattroruote states that thir motorway test is done respecting the Italian way of driving, with a few kick-dows acceleration to emulate overtaking - but how many?

And driving in Italy, if you keep the posted limit there is nobody to overtake, believe me.

 

I think in English you meant the word "biased", not "unbiast." Regardless of the difficulties of English, we have seen somewhat similar problems with USA automotive publications.

One of the better magazines, Consumer Reports, has a similar problem with their "City" driving. Consumer Reports have not published their 'route' and 'driving profile' but their City numbers are consistently low for all vehicles. Worse, they publish a "score" that only in the case of the Prius has no correlation to their published evaluation scores. "Magic."

In this case, the 2010 (aka., 2009 in Europe,) I have no problem with their high-speed metrics since it matches mine. I've not seen their low-speed numbers for the 2010 and given the problems seen with the USA "Consumer Reports," it seems to be an area where problems can easily arise.

FYI, we have credible evidence that there may be problems with the 1.5L Prius at very high velocities:

There is evidence that the 1.5L Prius has a distinct fall-off in efficiency as speeds exceed 65 mph. The 1.8L Prius has no evidence of a similar fall-off in efficiency.

Last winter, a group of diesel advocates, "Green Human", tried to sandbag the 1.5L Prius versus the Jetta TDI in an 8,000 mile test. They choose cold weather, drove East to West (against the prevailing winds) and high speeds only to find the milage difference was ~40 MPG for the 1.5L Prius vs 41 MPG for the Jetta TDI. In the USA, maximum highway speeds are ~75 mph (120 km/h.) They needed to exceed an average speed of 80 mph to "beat the Prius." <grins>

Bob Wilson

 

ALS,
How much a persons time is "worth" is a variable, only they can make that determination and of course that is a variable as well. But, the over riding truth is that mileage closely follows speed in steady state driving, if you want to consume less fuel per distance traveled, slow down. There are many other things that can be done, but speed is probably the biggest thing that can be done.

 

HI: I'm 3 days new with a 2010 II .. and with my now 106 total miles, it seems pretty obvious watching the screen, when the bar goes further to the right, your fuel use is going up. The manual DVD explains it, also. I averaged above 50mpg on my 75 mile drive home the night I bought the car .... 60-68mph.

 

High Speed Glide – Gen 3 Prius​

I recently drove from Sydney to Melbourne, a distance of some 800 km, in my Gen 3 Prius and decided to test my theory that it was possible to decrease fuel consumption and travel time by using a high speed glide technique.
Normally when travelling a highway I travel a little below the max speed limit for that road for the following reasons:
1.[FONT=&quot] [/FONT]It is easier and more comfortable to drive at a slower speed.
2.[FONT=&quot] [/FONT]It is safer to drive at a slower speed.
3.[FONT=&quot] [/FONT]It limits the chances of exceeding the speed limit on down hill slopes.
4.[FONT=&quot] [/FONT]It allows those driving at the speed limit to pass more easily.
5.[FONT=&quot] [/FONT]It reduces fuel consumption.
On a highway where the speed limit is 110 km/h I usually drive at 102 km/h and use cruise control to maintain that speed. With the Gen 3 Prius the cruise control automatically prevents a build up of speed (within reason) when going down a hill by using regenerative braking. The Gen 2 Prius does not do this.
High Speed Glide
The technique I decided to trial for a high speed glide was to watch the eco meter that is projected on the windscreen (the first time I have found a use for it) and during down hill sections of road when it showed no bar to the right of the fixed left-hand mark, to turned off the cruise control and let the car’s kinetic energy increase the speed of the car from 102 km/h to a higher speed. The idea was to prevent the bar from encroaching on the eco (sic) side of the mark by carefully applying pressure to the accelerator to hold the bar at or just to the right of the mark. When the slope of the road decreases and the car’s speed will decrease. When it drops to 102 km/h re-engaged the cruise control.
The Trial
I ran three tests. Firstly, I let the cruise control hold the car at 102 km/h. The second test over similar terrain I used the high speed glide explained above using sufficient power to prevent regenerative braking. The third test was to use the cruise control and determine what the fuel consumption was at 102 km/h over flat ground. All three tests were on a duel highway except for about 15 km which were on a normal highway with one lane each way. A stop was made for refreshments in each of the three tests. There was little wind over the entire course and the air temperature was 29-32°c.
Test 1.
Driving as I normally do at 102 km/h use cruise control.
I started just south of Sydney and finished at the Yass turn-off, a distance of 220 km and a gain of 370 m in altitude. The terrain was rolling hills.
Result - I averaged 4.2 l/100km.
Test 2.
Using high speed glide with cruise control set at 102 km/h.
I started from the Yass turn-off and finishing on the highway 5 km north of Albury, a distance of 260 km and a loss of 250 m in altitude. The terrain was rolling hills.
Result - I averaged 3.8 l/100km.
Test 3.
Driving as I normally do at 102 km/h use cruise control.
I started from 5 km north of Albury and finishing 20 km north of Melbourne, a distance of 295 km and a loss of 20 m in altitude. The terrain was relatively flat and high speed glides were not possible.
Result - I averaged 4.0 l/100km.
Trial Results
The results of the three tests indicate by using the high speed glide technique fuel consumption for a journey on an undulating road can be reduce by up to 0.4 l/100km and the time taken for that journey will be slightly less.
The tests also showed that undulating country increases fuel consumption by about 0.2 l/100km under cruise control conditions.
Although there was a change in height above mean sea level, the change is not considered big enough over the length of the journey to have any marked affect on the results.
The test results may not be valid for very hilly terrain for two reasons:
1.[FONT=&quot] [/FONT]The increase of speed in the glide could well exceed the road’s speed limit.
2.[FONT=&quot] [/FONT]Climbing steep hills in cruise control may unduly increase fuel consumption.
The projection of the eco meter and speedo readings onto the windscreen makes high speed gliding safe and relatively easy to use. The opposite may be true in vehicles that do not have this projection.

 

Excellent! I have some questions about the protocol and terms ... just the normal confusion between USA and Aussi English.

Replicating the effect of being in "N" on the downgrades?

Were the altitudes read out from the GPS, signs, or other means?

By "dual (sp?) highway," you mean a total of four lanes, two in each direction?

The "stop ... made for refreshments" were during each of the three legs? As a suggestion, I tend to use a tripmeter to record the 'steady state' segments so acceleration and deceleration are not part of the data. If a "refreshing stop" is needed, just record the three trip meter values when leaving (or memorize them and write them down when stopped.) Once back to speed, reset the trip meter for the next segment.

Overall, a good effort and well documented. It would have been nicer to have more 'steady state' segments so the increase in speed could be quantified. Also, having two segments per test leg would let us see how 'reproducible' the test protocol is versus a leg with a break in the middle. Still, a very good effort.

I look forward to the day when we can buy 'off the shelf' a combined GPS mouse and injector monitor. This will let us quantify speed vs fuel consumption vs grade. Add the ability to operate the accelerator and we'll have the ability to achieve an additional 10% fuel efficiency with little or no increase in elapsed trip time.

Thanks,
Bob Wilson

 

I have more than 35K miles on my 2008. During a trip from CT to FL and back, I found that 71 mph was the fastest speed where I could get reasonable mileage. At 72 mph the mileage started dropping quickly. I averaged about 52 mpg for the trip of 2100 miles.