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Interstate vs, State Hwy. 100 mile trip

Discussion in 'Prius v Main Forum' started by David Prius V, Apr 28, 2012.

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  1. David Prius V

    David Prius V New Member

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    Interstate vs. State Hwy. 100 mile trip

    We have a 100 mile trip (each way) we make every month or so to pick up or drop off our son at UF, I have read that the "sweet spot" for highway travel is 71 mph in the V (?). As an alternative to the interstate route, I could take the state highway system which is more scenic, but adds about 25 minutes each way, and includes a number of red lights with a mostly 65 mph speed limit. My question is will my gas mileage be better taking the road less traveled? Or, is a constant cruise at 71mph my best bet. I really don't mind the extra travel time.
    Thanks in advance.
  2. Wanderer

    Wanderer Hybrid neophyte

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    In my experience the slower you go the better your gas mileage gets. (assuming all other factors equal). I suspect taking the road less traveled will improve things but only you can decide if a few mpg is worth the extra time. I think the sweet spot is a little lower. I'd say more 55-62 but that may impede traffic depending on location. We have mostly 60mph speed limits around here so that is reasonable for my area. W
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  3. CLUBGUY

    CLUBGUY Member

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    Re: Interstate vs. State Hwy. 100 mile trip

    I really don't mind the extra travel time.

    The question is "how much fuel is being used" during that "extra twenty five minutes"..??
    Total "DIFFERENCE" in fuel used is the question...!!
  4. btcompute

    btcompute Junior Member

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    Re: Interstate vs. State Hwy. 100 mile trip




    It seems to me the only way to know the answer is to try both routes and see what happens.
    Compare the difference in cost of fuel to the extra time that the slower route will take, then decide what works best for you.
  5. David Prius V

    David Prius V New Member

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    Thanks. I've only had the car for a week. I thought the 71mph "sweet spot" seemed too fast. I guess there's a reason the hwy EPA estimate is lower.
  6. catgic

    catgic Master & Commander Hybrid Guru

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    David Prius V – The 71 MPH is a Rule-Of-Thumb “Sweet Spot†speed point, where fuel burn efficiency against the power curve of the 1.8-Liter engine is “Sweet.†Of course, if you went slower (lower RPM), like the 55-62 MPH Wanderer suggests, you would use less fuel. Conversely, going faster (higher RPM) would burn more fuel to achieve an increased power point higher up on the Power Curve. The 71 MPH “Sweet Spot†Rule-Of-Thumb is for use by drivers using only Prius v OEM instrumentation (i.e. no ScanGuage, Tachometer, etc) to pick a good cruise-travel speed for Interstate/Open Highway travel.

    Knowing this nominal “71 MPH Sweet Spot,†particularly in the State of Florida where the Max Legal Highway Speed is 70 MPH, gives fuel consumption conscious drivers some useful knowledge. It lets them know that traveling at a speed above the “71 MPH Sweet Spot†will cause them not only to burn more fuel per incremental additional MPH, but to burn it more inefficiently, from an added power point of view --- while chancing receiving a costly speeding citation.

    I am a long time resident of Florida who knows the Interstate and Off-Interstate alternative Tampa-To-Gainesville route(s) you are pondering. I do not think driving on the back roads alternates are worth increased Per Tank-Full MPG fuel economy you might gain weighed against added Point “A†To Point “B†trip time. If I were making the drive, I would take I-75 and travel at a Cruise Control Set Speed of 65-66 MPH. This would deliver you the best balance of MPG Fuel Economy vs Trip Time.

    I regularly travel up I-95 from the Space Coast to JAX, which is ~170-miles. If I am not in a hurry, I cruise along with the ECC set at 66 MPH. If I am in a hurry, I set the ECC at 71 MPH. The 5 MPH difference is worth about 12-15 minutes. Running with the ECC cruise set at 66 MPH (~47 MPG, Measured Per Refill Method) gains me about 2MPG on a Per Tank-Full Top-Off On Arrival basis, as compared to cruising at 71 MPH (~45 MPG, Measured Per Refill Method). At today’s gas prices, 2 MPG over 170-miles is worth about 75¢ worth of Unleaded Regular Gas, or a $1.50, for the round trip. :plane:
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  7. David Prius V

    David Prius V New Member

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    Great answer and information. Thanks very much.
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