800+ miles on one tank

Discussion in 'Gen 3 Prius Fuel Economy' started by Mark57, Jul 23, 2010.

  1. Mark57

    Mark57 Senior Member

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    This morning I finished my goal of 800+ miles on one 11.9 gallon tank.

    Between July 9th and July 23rd, I drove 805.2 miles on 10.731 gallons of 100% no-Ethanol 87 octane gasoline with an average mpg of 75.016 mpg and an average speed of 22 mph and tires t 37/36 psi. Temps have been 79° to 98° with dew point from 68 to 85 (very humid) and south wind consistently @ 15 - 20 mph every day.

    Before someone brings it up, note that I never over fill my tank and I always stop filling at the first pump shutoff. I carried a 2 gallon jug of spare gas with me at the end for safety purposes. It's not worth running out and I don't want to suck all the junk in the bottom of the tank onto the fuel pump intake screen. Been there did that years ago and had to pull the tank to clean the sock.

    Trying for high MPG is one thing but going for distance is nerve racking. I was sweating bullets towards the end. I drove about 70 miles past the flashing warning point. I was sweating bullets and that wasn't because it was 90+ degrees either.

    Early in this tank I had to drive about 60 miles with the A/C on so I'm surprised it went as well and as far as it did. I knew this tank would not break my record 76.4 MPG but it came close. I know I can do better but it's hard to block out 2 - 3 weeks to try something like this.


    [​IMG]

    The route I drove was comprised mainly of 45 - 55 mph rural roads with rolling hills. It was about a 35 mile rectangular circuit with stop signs, stop lights, traffic, and some 25 mph sections for school zones and neighborhoods. No, I didn't just go into a parking lot and drive in circles.:rolleyes:

    Here's a MapSource profile of one of the legs I drove on one of the days. Yes, it's flatter than Colorado but it's a heck of a lot hillier than Florida or Kansas.

    [​IMG]

    After all this, I'm ready to just drive normally for a while and enjoy it . . . . . Naaaaahhhhh.:D
     
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  2. efusco

    efusco Moderator Emeritus
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    nicely done...but even at the worst you only had a 300ft elevation change...can't complain about that.
     
  3. Mark57

    Mark57 Senior Member

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    Thanks Evan. I was just trying to show it's not flat as a pancake as many seem to think it is.

    What we may lack in total elevation rise on this route is somewhat compensated by the shear number of little 30 - 75 ft hills. They add up and wear you down on this type of run. Look at all those little spikes and dips inside the large 5 mile increments. There's not enough granularity on that graph to illustrate this very well.

    Here's the route profile for just this morning's drive. It shows all the little hills in better detail. It's basically a large rectangle including the area between Lake Hefner in northwest OKC to Piedmont, OK.


    [​IMG]
     
  4. efusco

    efusco Moderator Emeritus
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    BTW, how did you get/how do you know it's 100% gas w/o ethanol? I thought all the gas had some ethanol or other similar additive now.
     
  5. F8L

    F8L Protecting Habitat & AG Lands

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    Congrats Mark!

    I see you are running near manufacture's recommended tire pressure. What is your reasoning behind this decision? :)
     
  6. F8L

    F8L Protecting Habitat & AG Lands

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    I like the idea of using Mapsource to show your route topography. I'm going to try and figure out how to use it on my Garmin Nuvi 660. It looks confusing though. :confused:
     
  7. Mark57

    Mark57 Senior Member

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    The Oklahoma Corporation Commision requires all gas stations to post whether their fuel contains Ethanol. The stations learned very quickly that most everyone wants the no-Ethanol fuel so they post huge signs that they sell only 100% no-ethanol gasoline. Fortunately, we still have a choice fuel here. It makes a difference.

    I tried higher pressures in the 40's range here at home and on a trip I did down to Big Bend, TX. I've been road racing bicycles since I was a teen so i know about the benefits and lower rolling resistance of high pressure tires so this will sound weird.

    When I tried the higher pressures, it did not increase my mpg's here. They didn't go down either but the ride was MUCH worse. We have a lot of very rough roads in the area where I do my test drives. Also on the Big bend trip I drove the same identical route twice. The asphalt roads there are almost like small cobblestones and at 40+ psi teeth jarring. The round trip leg from Fort Stockton down and back at 40 psi did not increase my mpg but when I reduced the pressure back to 37/36, my mpg went up by 5. So I concluded that in an environment of rough roads, high psi may not always be beneficial.

    See my post #11 and #16 in this thread for a better description. http://priuschat.com/forums/gen-iii...tire-pressure-what-your-psis.html#post1145284
     
  8. Mark57

    Mark57 Senior Member

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    I also have a Nuvi. Just download the track from the Nuvi using mapsource on your PC. Then right click and select properties on that track and then select show profile.
     
  9. F8L

    F8L Protecting Habitat & AG Lands

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    Great, thanks!

    As for tire pressure. I usually run very high pressure (50+psi) but I am currently running 44/42psi because I just swapped from my 17" wheels back to my 15's and found I rather like the smooth ride and wanted to try running the lower (for me) pressure and see how my mileage works out. So far I am still able to maintain 50+mpg as long as I exclude my work commute due to high elevation gain. i.e. my mileage is still high despite lower tire pressure. :)
     
  10. Mark57

    Mark57 Senior Member

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    That's good that your mileage is staying high.

    I'm going to try the high pressure again. My mind says it should make a difference. i need to test it again.

    My wife's Altima has the 17" baloney skins and they are rough riding.
     
  11. Judgeless

    Judgeless Senior Member

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    Same here, Congrats Mark!

    Why are you keeping the tire preasure at the mfg recommended presure? If you filled them to 49/47 PSI you might be able to get 900 miles on a tank of gas.
     
  12. Mark57

    Mark57 Senior Member

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    Thanks! I talked about the psi changes in post #7 above. Tried it before and it didn't improve mpg. I didn't hurt other than loosening my teeth but it didn't help so I went back to 37/36. I'm going to test with the higher psi again. I know logically, it should help but on these rough roads it just hasn't.
     
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  13. Tideland Prius

    Tideland Prius Moderator of the North
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    well done! That is quite impressive and something for the rest of us to aim for (if possible...).
     
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  14. Mark57

    Mark57 Senior Member

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    Thank you. I only started out aiming to break my previous mpg record but because of some early A/C usage it was not high enough early enough so I then changed my goal from mpg to 700 miles but I still had 31 miles DTE around 700 so I went for it. I'm not sure I have the nerves or sphincter strength to go for 900 miles.;)
     
  15. Dan bo

    Dan bo Prius Fan

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    Wow that's about all I can think of saying Mark ...WOw 800 miles, very scary and impressive. I don't think I could ever nurse 700 out of mine, but very happy when I do get 600.

    Running about town I find that the shutdown and start up kills my mileage, how do you get around that?
     
  16. Mark57

    Mark57 Senior Member

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    Thanks Dan! Consider that I did this over a two week period and I was specifically trying to break my mpg record again. That means no unusual trips or short trips for that time. (hard to do for two weeks)

    I did have to start out cold every day and my average mpg would drop until the S4 stage or so and then I'd try to build it back up to at least where it was when I started that day and increase it if possible. I would not go back home until I recovered/improved the lost mpg each day.

    Early on in this tank I had quite a few miles (~60) with the A/C on so it became apparent that I was not going to break the mpg record so i started focusing on distance. My mpg was in the high 70's when i went past 700 miles and my DTE was something like 31 so I decided to shoot for 800. First I got a gas can with 2 gallons in it to carry with me. I was still nervous even with the gas can.

    I started out around 4:40am on rural roads so I would not be a traffic hazard. The traffic would pick up around 7am or so and I make sure I was going the opposite direction at that time.

    Start up and shut down is tough though. I do allow the car to warm up to it's ~112° (when it shuts off) before moving in the mornings and I also try not to run the battery down to 2 bars at night so i don't have to fight that the next morning with a cold inefficient engine. It helps a lot.
     
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  17. Dan bo

    Dan bo Prius Fan

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    Thanks for the info Mark! I agree about "tying" not to end the day with only 2 bars, been then done that too many times, payback the next day is a b#tch!

    I give you credit for getting to the 800! a fair amount of work and planning. But it is pretty cool to think that you can drive this car like any other and still easily get 500-600 miles. :cheer2:

    Enjoy the day
    Dan
     
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  18. Mark57

    Mark57 Senior Member

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    Thanks Dan and you are absolutely right. It's an amazing vehicle. You can drive it like a maniac and get 45+ mpg or 500 miles to a tank. I do so enjoy "playing" to see how far I can push the vehicle's capabilities (safely). It makes driving fun.

    I've brought my psi back up to 42/41 and am testing how that does. So far so good.

    Have a great weekend.
     
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  19. windstrings

    windstrings Certified Prius Breeder

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    I used to run high tire pressures.... close to 60... now I run 42 in front and 40 in back.. notice no notable change... but being as critical as you were in your test, I"m sure you would notice some difference.

    I figured it just wasn't worth the risk after my blowout.
    I simply grazed the edge of the road where the blacktop was broken and it hit one of the spots and "pop"!.

    With the crazy hot temperatures we get here, I need my tires saving me in an emergency.. not "being" the emergency!
     
  20. mgb4tim

    mgb4tim Noob

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    and I was doing cartwheels yesterday when I calculated 48.7 MPG... I love the hills in Pittsburgh ;)
     
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