To Cruise Control or not to Cruise Control

Discussion in 'Prius c Fuel Economy' started by iBO, Mar 24, 2015.

  1. iBO

    iBO New Member

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    I just got a new 2015 Prius C Three and have been reading up as much as possible. I wanted to know if using cruise control would give me better MPG. If it's just a matter of 3/4 mpg difference, then I would use the cruise control to rest my feet. But if its a big difference, then I would avoid cruise control.

    My daily commute from Germantown, MD to Alexandria Va and back is about 40 miles each way: total 80 miles. 90% of that highway on I-270 and I-495. I leave after morning rush hour and again drive back after evening rush hour.

    Last couple of trips without cruise I have been getting around 50~52mpg.

    Thanks.
     
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  2. bisco

    bisco cookie crumbler

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    i use cruise. if it gets really hilly, and i feel motivated, i'll shut it off and use some manual techniques, but i don't think you save enough to do it all the time on a long trip.
     
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  3. fuzzy1

    fuzzy1 Senior Member

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    Just try it and find you what it does for you.

    The impact of CC depends on both the driver and the particular conditions. It will often help 'average' drivers, but never help the best hypermilers.
     
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  4. The Electric Me

    The Electric Me Go Speed Go!

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    2 speeding tickets in less than 12 months means I use cruise control....because I have to.....

    It is what it is.
    I think on long drives, freeway stretches, it's a nice tool, primarily of comfort.

    I think in most cases, once you are familiar with the vehicle you can meet or exceed the MPG on a long drive that you get with the cruise control. But I don't really factor that into my decision to use it.

    Case in point. On a highway with a sudden or even slight incline, if I'm in cruise control, the cruise control is going to work to keep my speed at whatever MPH I have set. So if I'm suddenly going up a hill, it is going to power up to maintain speed. And for that stretch my MPG will decrease.

    If I'm controlling the speed? I can choose to slow down for that stretch, realizing it is only temporary. While my speed may decrease slightly for that stretch, I can keep MPG pretty consistent.

    Cruise control is a tool, and I think a great tool. But radar cruise control aside? It's only a tool and only as smart as it can be.

    Fear of somehow forgetting and accidentally getting another speeding ticket has me using Cruise Control a whole lot more than I normally like. It's nice to be able to set it...and know you aren't going to get pulled over because you didn't noticed you picked up significant speed. But as a tool? I think use it, or don't use it, it's up to the individual.
     
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  5. bisco

    bisco cookie crumbler

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    i used it all the way to florida and back, whenever possible. we pulled 46mpg in the hycam, from nc to nyc, don't ask me how.
    the hills of connecticut are particularly steep and short, (for the east coast) and cause a lot of unnecessary revving, imo.
    i tend to do as em says above, speed up a bit before hitting the hill, and slowing a bit when climbing, in the right lane and if traffic allows.
    it's also necessary to use manual as cars enter the highway to merge, if you're in the right lane with me.:)
     
  6. Mendel Leisk

    Mendel Leisk Senior Member

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    From the instant mpg numbers I see on ScanGauge while using cruise, I'd be hard pressed to do any better; the cruise uses a very light touch to maintain speed. Obviously if you're going to let your speed fall off on an upgrade then you can do better, the cruise will try to adhere to the set speed. But on level roads it's good; I use it quite a bit.
     
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  7. mmmodem

    mmmodem Taste Tester

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    Whether CC is better for fuel economy depends on your individual commute. It's highly YMMV. You'll just have to experiment and find out. Generally, hills and valleys favor no cruise control for best fuel economy.

    For my commute, I CC as much as I can but there are certain sections I turn it off. If going downhill forces CC to regenerate battery, I step on the gas to make sure HSI is right of the line. If uphill forces CC to go into the PWR zone, I turn it off until I crest the hill.
     
  8. The Electric Me

    The Electric Me Go Speed Go!

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    Honestly I agree.
    I think cruise control is great.

    But basic cruise control is just maintaining any set speed.

    The obvious weakness of cruise control is the inability to actually "see the road" or upcoming changing parameters.

    If I'm going up a 1/2 mile incline, that then goes downhill or levels off? It doesn't know this, and is going to use as much engine power and gasoline as possible to keep my speed consistent. While obviously if I'm driving I can ascertain the benefit of just losing a little speed until I get over the rise.

    Maybe I'm kidding myself, but I think I can do as good or better as far as MPG if I'm actually "non-agressively" controlling the acceleration/deceleration if only because I can make decisions based on what I actually see ahead.

    I use Cruise Control primarily as a tool of convenience and long distance driving comfort.

    These parameters might be different if using "Radar Cruise Control" which still strives to maintain a set speed but WILL adjust to the changing speed and parameters of any vehicle ahead of you.
     
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  9. frodoz737

    frodoz737 Top Wrench

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    The biggest thing affecting mpg on this commute is your cruise speed, manual or CC. Sure you can P&G or do the roller coaster thing on hills and do better, but this is not the kind of thing other commuters take kindly to...especially on the freeways...even if you work graveyard like I do. Since you asked...I say find the sweet spot your comfortable with, set it and know your doing better than most out there already.
     
  10. iBO

    iBO New Member

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    Thanks everyone! Last couple of trips I have been driving without Cruise between 60-65mph. I will try 65mph with Cruise. It's not exactly flat. There are a few inclines.. up and down but not too steep.
     
  11. frodoz737

    frodoz737 Top Wrench

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    If your traffic pattern "allows" cruising at 60-65 mpg, then your good either way. Happy motoring.
     
  12. Dimitrij

    Dimitrij Active Member

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    On a relatively flat road, cruise control should not affect the mpg. When going uphill it will likely cause you use more fuel, because it will attempt to maintain constant speed even when a human driver would allow the vehicle to slow down to prevent the engine from going into higher (and less economical) rpm.
     
  13. iBO

    iBO New Member

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    So it seems that difference between driving at 65mph and 60mph, both times on cruise control, is striking! In, my commute more than 95% is highway and I think 90% of that was set on cruise control.

    The trip I took at 65mph gave me 47mpg, and the trip I took at 60mph gave me 57mpg!

    I am sure 55mph would be even better, but it would take me ages to get to work or back home. I was used to driving 75mph on average until I sold my Altima last week and got the Prius C. 60mph is the slowest I can take at the moment :)
     
    #13 iBO, Mar 26, 2015
    Last edited: Mar 26, 2015
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  14. frodoz737

    frodoz737 Top Wrench

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    I did 60 mph on a trip once to see what I could get and was surprised with my best ever of 61.9 mpg. The problem however is traveling this speed on an Interstate, especially between cities where it only becomes two lanes each side, is not conducive to safety or friendly driving manners. I pissed off everyone, but imagined (briefly), what could I have achieved doing the minimum speed limit of 45 mph? The point is a trade off must be made. While some areas and situations are favorable to maximizing bragging rights, safety must still be the foremost precedent within the "real" traveling world. I think one of the reasons Prius owners still to this day are prejudiced for being road blocks is because of those few that have or still play the meter game. Bottom line, even going 75 mph you still beat everyone else's commute cost. Anyways...enjoy discovering your new toy and best wishes. ;)
     
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  15. fuzzy1

    fuzzy1 Senior Member

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    The lack of safety and friendliness at that speed is specific to the road culture of particular localities and regions.

    There are other regions and localities where that speed is quite acceptable. The road cultures are different.
     
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  16. frodoz737

    frodoz737 Top Wrench

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    Indeed there are...but I did not see it the two week I was in Cincinnati. Unfortunately the reality is most major cities and most major Interstates are not "slow drive" or "P&G" friendly/safe. I made every effort to be respectful, balanced and friendly with that post. ;)
     
  17. Easy Rider 2

    Easy Rider 2 Senior Member

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    I also found out that it depends to some degree on the vehicle that you are driving.

    Doing -5 to-10 on the Interstate in the right lane DRIVING A BIG, HULKING RV didn't seem to cause any problem at all.

    I think it has to do with other drivers EXPECTING that kind of speed out of them and maybe thinking that's all they can do.

    Other drivers seem to move over to pass a LOT farther back than they would have done if I was in my Prius.

    P.S. 65 isn't all I CAN do but it is all I am willing to do. 8 MPG is bad enough.
     
  18. Dimitrij

    Dimitrij Active Member

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    As per the pump, or per the ECO indicator? My indicator stubbornly exaggerates the mpg by 6%.
     
  19. fuzzy1

    fuzzy1 Senior Member

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    I haven't found anyplace in my entire state were 60 mph is unsafely slow. In numerous places, average speeds are indeed higher, especially in the I-5 corridor between Seattle and Tacoma. But there are still enough vehicles obeying the speed limit, whether for fuel efficiency or as a condition of continued employment, that others can join them without feeling heavily pressured to go faster.
     
  20. iBO

    iBO New Member

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    I guess its the ECO indicator. I got the numbers from the trip summary when I turn off the engine.
     
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