Crazy mpg hit with cargo box

Discussion in 'Gen 2 Prius Main Forum' started by MattyD., Mar 24, 2021.

  1. MattyD.

    MattyD. Junior Member

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    Hey guys, anyone have experience with cargo boxes? I'm preparing for a roadtrip from Oregon to Michigan and back(about 5k miles total) and want a bit more storage space. I purchased a used rack as well as cargo box but the box dropped my highway fuel economy from 45 to 33. From my calculations, this would add about $300 to the fuel bill for the trip.. 20210323_170141.jpg 20210324_125048.jpg 20210324_125251.jpg I know it's a large box, anyone know what kind of hit I'd get with a smaller more aerodynamic box? Or would I be better off ditching the rack, getting a hitch mounted and going with a hitch mounted box? If so what kind of hit would that do?

    Thanks for any input and advise.
     
  2. PriusCamper

    PriusCamper Senior Member

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    How often you're driving on the freeway defines how bad the loss in MPG... And compared to how many options you have once you install a hitch on the back, I'd always go with the hitch and never the top of the car.
     
  3. Sanchan

    Sanchan Junior Member

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    That is a giant roofbox! I would be thinking about something like these if I don't want to buy a hitch!
     
  4. Formula_Ron

    Formula_Ron Junior Member

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    I have that exact same roof box :LOL:. I've never put it on my Prius and always wondered how it would look. It's surprising how much your mpg dropped... Thanks for posting pics.
     
  5. mr_guy_mann

    mr_guy_mann Senior Member

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    As long as you don't have too much weight to carry, I would think that a hitch mounted box would have way less mpg impact. Access to the tailgate is another consideration.
    It's not just tbe aero affect of the roof mounted box itself.
    It's how much it screws up airflow over the roof and makes a huge "dead space" behind the car.

    Posted via the PriusChat mobile app.
     
  6. Mikhail Bond

    Mikhail Bond Member

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    I'm getting about 38.5 mpg. With oversized tires. I had that same box and ended up switching to the Thule one and spent that extra 300 dollars on a better box IMG_20210322_091602.jpeg

    Posted via the PriusChat mobile app.
     
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  7. PriusCamper

    PriusCamper Senior Member

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    Can you tell us more about your tent in the back? Doesn't look like a habitent, but something different?
     
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  8. Sanchan

    Sanchan Junior Member

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    Nice! where is this campground?
     
  9. SeattleBebop1

    SeattleBebop1 Member

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    Damn, the box is a huge hit. I've got oversized all-seasons (27" instead of the 25" Ecopias) on my lifted car, and my hit is maybe 2-3 mpg at most. Like I still get about 50 mpg going 70-75 mph, and going 65 mph it's more like 53 mpg (referring to gasoline engine only, I can only charge my battery once a week).
     
  10. Mikhail Bond

    Mikhail Bond Member

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    It's a riteline from REI
    https://www.google.com/aclk?sa=l&ai=DChcSEwjpqOSX5c7vAhWlPa0GHUOpALoYABAHGgJwdg&sig=AOD64_0K_YfPteqxgsvoFRiLfoM7UkPtdA&ctype=5&q=&ved=2ahUKEwihwtuX5c7vAhWBFjQIHftNAQAQwg96BAgBECo&adurl=

    It worked for that trip but I don't recommend it because the pole sleeves are made of mesh,

    Also, if you plan to RDY mode your engine, make sure to either modify your exhaust to output on the right side or dryer hose it.
    Posted via the PriusChat mobile app.
     
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  11. Mikhail Bond

    Mikhail Bond Member

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    This is El Capitan along the 101 freeway just north of Santa Barbara california.
    You can usually grab a spot no reservation if people don't show up. They have a list posted at the booth everyday.
    Posted via the PriusChat mobile app.
     
  12. PaulDM

    PaulDM Active Member

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    BC198B7E-F167-4005-8D43-CEB41D9B7877.jpeg

    Yup. You lose about 10mpg with a top box
     
  13. Sanchan

    Sanchan Junior Member

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    Ok! No wonder it looks a bit familiar... I think I camped there once maybe....15years ago(I was on my motorcycle). Thanks for your reply! My first day of camping(of any trips)are usuall at San Simian outside of Cambria on PCH up north! Not as spacious as El Captian but I love a morning drive beetween there and Big Sur!
     
  14. w2co

    w2co Member

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    I still have an 06' that gets 60 mpg on a good day, and I've tried the hitch thing, talk about a mpg hit! Guess it depends on what you're pulling there. That roof rack looks like it will absolutely ruin the aerodynamics of the car thus your mpg hit. If I were going on a long trip and had a few things to bring, I would fold down the rear seats. That will give you plenty of room for things ( I have fit a 6' door in there) but you can only have one other person with you ie; the passenger front seat. If traveling alone, that's even better!
     
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  15. MattyD.

    MattyD. Junior Member

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    Update: I sold that box to my sister who has a Honda pilot and purchased another smaller more aerodynamic box and it's an improvement. Freeway, cc locked at 69mph puts me at 37 mpg. Definitely more of a cut then I'd like but I think it's worth it for the space. 20210326_141312.jpg
     
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  16. MattyD.

    MattyD. Junior Member

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    My goal is to get a lift, new struts and mounts and possibly tires this summer. Hopefully I can still get 40. Rn without the box, I can get about 45 if I keep it to 70.
     
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  17. SeattleBebop1

    SeattleBebop1 Member

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    Yeah, it's still better than your average SUV at 40. I will never return the kinds of numbers like the hypermilers here, which I'm a bit jealous of, but the most important thing to me is to have a car that I can use for hiking that gets good enough mileage. Good enough that I don't feel too guilty about burning fuel... and I do pretty long road trips for my backpacking too so spending less is nice.
     
  18. TinyTim

    TinyTim Active Member

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    I consider it a crime to get anything less than 50mpg on the highway in a Prius. With that said, any box has to go if the mileage takes a hit.
     
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  19. PriusCamper

    PriusCamper Senior Member

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    It is true... They build sports cars to go really fast, they build trucks to haul heavy stuff and they build Prius to get the very best MPG possible. Those who get bad gas mileage in their Prius do a grievous dishonor to their Prius and our community! We need to ban them if they're unwilling to change their ways!
     
  20. SeattleBebop1

    SeattleBebop1 Member

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    Now now, even a Prius with lower MPG is still producing lower emissions! And performing the social good of annoying Prii haters...
     
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