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2006 Highlander Hybrid MPG discussion and mods

Discussion in 'Toyota Hybrids and EVs' started by drewbabich, Mar 6, 2014.

  1. drewbabich

    drewbabich Junior Member

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    Vehicle:
    2006 Prius
    Model:
    II
    My HIHY 2006 gets great gas mileage below 50 mpg in suburban driving (taxi use, otherwise it'd be impractical to really justify enough driving at these speeds to build up enough miles to make a big savings from this type of driving)

    On the highway I'm quite dissapointed that the hybrid can't magically overcome wind resistance forces at 75mph and save me some MPG's. Last night in 200 miles of driving at 16 degrees F (i had the heat off), I was getting around 20 mpg at 75 MPH avg. I was north of boston so it wasn't perfectly flat, but it was still I95 highway and smooth rolling hills. It appears the battery barely ever kicks power over to the electric motors over 65 mph.

    I'm running 87 octane, tires pumped to 39 PSI and the roof rack cross beams are removed to decrease drag.

    I can get 27 to 30 mpg if I baby it below 45 mph, but on the highway this thing really seems no different then most any other suv.

    My 08 kia borrego can get 17-20 mpg on the highway in these winter conditions and that thing is a giant tank compared to my HIHY.

    Granted in stop and go taxi use my HIHY can return 24 mpg in winter compared to 16 mpg in the Kia, but I'm still disspointed to get such pathetic highway mpg's.

    My 04 prius will get 40 plus mpg on the highway which is way more exciting but it is A.)real loud with wind noise over 60 mph and b.) not as accomodating to 5 extra passengers with luggage.

    How do other people do in the winter with their HIHY on the highway. I try driving at 60 to 65 mph, but its not practical, loss of valuable time is more expensive then the drop in economy.

    I just feel like a minivan would get better highway mpg then the HIHY which is pretty sad to me.
     
  2. jdenenberg

    jdenenberg EE Professor

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    Your problem has multiple causes:
    • Poor Highlander aerodynamics
    • Large displacement engine (compare it to your Prius 1.5 liter ICE)
    • Probable excessive rolling resistance tires There are LRR tires that can save 5-10% MPG over normal SUV tires and stay away from "Drive Flat" tires which kill MPG.
    • Driving too fast - Aerodynamic losses go up with the cube of velocity.
    JeffD
     
    Meg&Bear likes this.
  3. drewbabich

    drewbabich Junior Member

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    I hear ya jeff. I know 75 mph is bad news in an suv, but 20 just seems extra weak. And the tires are 16" 225 passenger car style tread tires.

    My kia has 18" 265 beefier passenger tires.

    The highlander still has a smaller ICE 3.3 vs 3.6 for the borrego and when you look at them parked side by side the two cars are night and day in size. The borrego is bigger then an explorer and I think and the Highlander looks like its about the size of a Forester.

    You'd think the highlander would at least make an attempt to shut the ICE down and use some of that FULL battery on the highway, but it never seems to care.

    I had the heat off for crying out loud. I'm just hoping in the summer it does a lot better.

    I know Toyota is the king of hybrids and love what the prius magically pulls out of its bag of tricks. But this highlander, on the highway at speed, shows its possibly less efficient then my kia borrego when you factor the extra size, mass and larger tires that Kia has.
     
  4. jdenenberg

    jdenenberg EE Professor

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    It's not just the size of the tires but how they are constructed. LRR tires have a rubber compound in the tread that stays soft in cold weather and generates less heat when flexed. They replace the carbon with organo-silicates to get this effect. Take a look at Nokian WRg3 tires.

    JeffD
     
  5. markabele

    markabele owner of PiP, then Leaf, then Model 3

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    Drew,
    The engine will never shut off at highway speeds. It would become less efficient if it used the battery at those speeds since it would just have to fill the battery again via energy from the engine.

    Also, do you practice a pulse and glide technique when you are driving at slow speeds around town?