1. Attachments are working again! Check out this thread for more details and to report any other bugs.

I've finally found the secret to increase mpg

Discussion in 'Gen 2 Prius Fuel Economy' started by wintechsw, Aug 16, 2009.

  1. wintechsw

    wintechsw Junior Member

    Joined:
    Jul 19, 2009
    36
    8
    0
    Location:
    Vic Australia
    Vehicle:
    2010 Prius
    Model:
    N/A
    Background: 1. My experience is 31000km in a base II model with Lifetime Average of 20.4 km/litre or 57.5 mpg(Imperial) in Oz, mainly long distance driving at 110kph speeds on Cruise Control uphill downdale. That's 48mpg for US measuring. 2. I have a ScanGuage II installed and have one of 4 settings to display LOD which is the engine loading. My observations are that the consumption falls dramatically when the LOD is 79 or greater. So my key to Economical motoring is to keep the LOD figure below 79 at the maximum speedo reading. 3. I went for a 330km trip yesterday over fairly flat terrain, sat on 110kph(113 on the speedo) and averaged 5.2l/100km. On my return trip, after refuelling, I set my speedo at 106(actual 104kph) and the consumption average dropped to 4.7l/100km. The LOD stayed below 79 for most of the way, occassionally going over that figure for uphill gradients. 4. Coincidentally the displayed engine RPM stayed below 2000rpm whilst the LOD was below 79(not a surprising fact), but it still fluctuated wildly for level running. At 110kph, the RPM varies greatly from 2100rpm to 2500 rpm at every SGII refresh.

    My maximum freeway speed will now be set at Cruise Control 106kph.
     
    #1 wintechsw, Aug 16, 2009
  2. krousdb

    krousdb NX-74205

    Joined:
    Jul 16, 2005
    580
    498
    47
    Location:
    Raleigh, NC
    Vehicle:
    2016 Prius
    Model:
    Two
    What you have discovered is that aerodynamic drag increases exponentially as your speed increases. At 106kph, you have not yet found the sweet spot. Try 88kph. You will be amazed.:D
     
    #2 krousdb, Aug 16, 2009
  3. spinkao

    spinkao New Member

    Joined:
    Jul 27, 2009
    316
    76
    0
    Location:
    Czech Republic, EU
    Vehicle:
    2008 Prius
    Model:
    N/A
    Krousdb is right. You are also correct that the engine is most efficient when working under certain load; Try to read this very interesting article by Hobbit:

    Prius throttle control

    If 88km/h is sufficient for you, you will get amazing results at that speed (assuming flat ground, no wind). Your consumption at that speed can get as low as about 3.2-3.5l/100km average, sometimes even lower. I regularly manage to repeat that feat when traveling some 55km at that speed on the highway from my apartment to my parents' house. I also try to travel behind a large truck if possible, in order to try to reduce air resistance. Of course, I always keep a safe distance behind him, which compromises the efficiency a lot, but safety should always be at the first place.

    Using this technique and well-known hypermiling tricks in the city, I regularly get 4.2l/100km per tank, including short commuting trips through the city, which are a real consumption killer. You can get significantly better than that if you can avoid short trips, which I, alas, cannot.
     
    #3 spinkao, Aug 16, 2009
  4. wintechsw

    wintechsw Junior Member

    Joined:
    Jul 19, 2009
    36
    8
    0
    Location:
    Vic Australia
    Vehicle:
    2010 Prius
    Model:
    N/A

    Yes I agree the consumption mpg increases with reduced speed, but the tradeoff is the time difference for the trip which is from 7 mins to 45 mins of increased travelling time.
     
    #4 wintechsw, Aug 16, 2009
    1 person likes this.
  5. krousdb

    krousdb NX-74205

    Joined:
    Jul 16, 2005
    580
    498
    47
    Location:
    Raleigh, NC
    Vehicle:
    2016 Prius
    Model:
    Two
    Agreed. We all have to make that decision. I would save 20 minutes a day if I increased my speed to 106kph. But saving 20 minutes does not mean that I will earn more money. It just means that I have some spare time on my hands. My choice is to give up some spare time so that I can spend less of my hard earned money supporting OPEC. It works for me.:D
     
    #5 krousdb, Aug 16, 2009
  6. JimStPete

    JimStPete New Member

    Joined:
    Jun 29, 2009
    3
    0
    0
    Location:
    Clearwater FL
    Model:
    V
    :usa2::usa2::usa2:
     
    #6 JimStPete, Aug 16, 2009
  7. donee

    donee New Member

    Joined:
    Aug 15, 2005
    2,956
    197
    0
    Location:
    Chicagoland
    Vehicle:
    2010 Prius
    Model:
    III
    Hi wintechsw,

    You have rediscovered SHM - Super Highway Mode. Do a search on SHM here, and on CleanMPG.com for complete details.
     
    #7 donee, Aug 16, 2009
  8. richardp

    richardp New Member

    Joined:
    Sep 4, 2009
    12
    0
    0
    Location:
    New Port Richey, Florida
    Vehicle:
    2007 Prius
    Model:
    N/A
    What's a ScanGuage II ?
     
    #8 richardp, Sep 9, 2009
  9. direstraits71

    direstraits71 Member

    Joined:
    Jul 17, 2008
    367
    64
    0
    Location:
    Central Coast California
    Vehicle:
    2008 Prius
    #9 direstraits71, Sep 9, 2009
  10. 13Plug

    13Plug Active Member

    Joined:
    Apr 7, 2008
    581
    104
    0
    Vehicle:
    2013 Prius Plug-in
    Model:
    Plug-in Base
    The biggest difference I've seen in the last few tanks of gas is due to the fact that I've held the accelerator steady on the highway, don't use cruise, let the car speed up and slow down as appropriate (I keep it at 5.0 or lower, thus speed is around 100 km/h).

    I saw an increase in economy from 5.4 - 5.7 down to 4.8 - 5.1 L/100km. Give that some thought, just focus on keeping your consumption on the highway below 5.0 and don't worry as much about the speed.
     
    #10 13Plug, Sep 10, 2009
  11. Dan.

    Dan. MPG Centurion

    Joined:
    Sep 7, 2005
    387
    127
    1
    Location:
    Houston, Texas
    Vehicle:
    2007 Prius
    Yes, I second that. Keep throttle SOLID without bouncing the pedal. If you have a ScanGauge you can program it with a "gas pedal pressure" gauge that will help you control your right foot. When you see the read-out you'll be amazed how much most people bounce the throttle without even realizing it, and Cruise Control is practically a "random throttle generator". Not good for MPG.

    11011011
     
    #11 Dan., Sep 10, 2009
  12. namasteflc

    namasteflc New Member

    Joined:
    Apr 16, 2009
    47
    5
    0
    Location:
    Georgetown Md
    Vehicle:
    2010 Prius
    Model:
    II
    Back in the good old days, some vehicles had 'hand throttles' that held the accelerator; an early form of cruise control.
    Frank
     
    #12 namasteflc, Sep 10, 2009
  13. eagsc7

    eagsc7 Geocacher

    Joined:
    Jul 23, 2008
    50
    3
    0
    Location:
    Prescott, AZ
    Vehicle:
    2010 Prius
    Model:
    ----USA----
    ... 45 Minutes IF you are driving Over 400 Miles Per Trip. Yes, I did the math.

    Most people will Think that they are Saving time by driving faster... I have found out that 1 or 2 Stoplights WILL take out All the time that you save by driving faster. Yes, this HAS been tested by three vehicles at the same time. the First vehicle had a speed of 70, The second had a speed between 63 and 68, the Third was mine that I set Cruise control at 55. I caught up with the Second vehicle at the First stoplight, and the First at the Third stoplight... The total drive distance for this test was 58.2 miles.

    Oh, and As for anyone that asks..."What kind of Miles per Tank will driving 55 instad of 65 do?" That test I have also done in a rather fun manner. Both were done in the Same weather conditions, and over the same driving area. Driving 55, I got 630 Miles before the car gave the traditional Triangle of Death! Driving at 65, I only 470 Miles before the same triangle. This would be obvious for me to say that YES, I filled the tank to the same 11.85 Gallons both times(this is where you can actually SEE the fuel in the inlet).


    The Steaks
     
    #13 eagsc7, Sep 25, 2009
(You must log in or sign up to post here.)