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High fuel consumption WHILE coasting with charge available?

Discussion in 'Gen 3 Prius Fuel Economy' started by Kelly McDonald, Aug 9, 2016.

  1. Kelly McDonald

    Kelly McDonald New Member

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    Location:
    Delhi, Ontario
    Vehicle:
    2012 Prius
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    ----Canada----
    When I go out to do errands around town (I live right in town) I get horrendous gas mileage. Now, I understand gas mileage is high at the beginning of a trip, but for this long and this high and under these circumstances? I'm getting ABOVE 10l/100km when I have 80% charge available (for americans, that's disgustingly high MPG like, pick-up truck high), AND my foot is completely off the gas. Literally, coasting, or braking, and I'm still sucking up gas. What the heck? Is this just because it takes a certain amount of time for the engine to run no matter what or something? I still don't see any reason for me to be eating up all that gas when my foot isn't even on the gas AND most importantly, I have charge available. Feels pointless for me to use my car for what I use it for 70% of the time, which is for quick errands around town at low speeds. Thought the prius was suppose to be a superstar for this kind of thing.
     
    #1 Kelly McDonald, Aug 9, 2016
  2. RRxing

    RRxing Senior Member

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    Short trips are one of several MPG killers.
     
    #2 RRxing, Aug 9, 2016
  3. fuzzy1

    fuzzy1 Senior Member

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    When this happens, is the engine fully warmed? If not, the engine will run (or restart, if it has cooled down) to get up to operating temperature. This happens regardless of battery charge. If you are moving slow, or stationary at an intersection, your consumption reading will be very high.

    This can also happen when the exhaust catalyst needs to reheated, even when the engine temperature is fine.
     
    #3 fuzzy1, Aug 9, 2016
  4. Tideland Prius

    Tideland Prius Moderator of the North
    Staff Member

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    Are you driving in "D" or in "B". If you're in "B", that might explain your fuel consumption. I've never seen 10L/100km (that's 23 US mpg). Even in the dead of winter with -40°C for one week during that tank, my tank average was 6.1L/100km (38.6 US mpg).

    Also, it takes a while for the engine to warm up (about 2 mins in the summer. Much more in the winter). How long are your trips? If they're all less than 5km, then you're not going to get good mileage. I had one tank start out as poor as 9L/100km because I was doing short trips, in hilly terrain (so I always seem to be starting at the bottom of some hill) and trips were all less than 10km.
     
    #4 Tideland Prius, Aug 9, 2016
  5. bwilson4web

    bwilson4web BMW i3 and Model 3

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    There is a checklist hanging around of things to do. I don't have ready link but maybe someone can post it for you. It is good to make sure the 'usual suspects' are not involved.

    Also, Delhi is pretty small. As a general rule, the car has to travel at least 1-2 miles before it is warmed up enough to begin returning good mileage. Even then, the good MPG has to average with the existing "warm-up" cost. As a general rule of thumb, 8-10 miles, 13-16 km, is the distance to start seeing good MPG.

    One thing I like to do is compare the car to an earlier benchmark to make sure it is OK:
    [​IMG]
    • Find a loop or a route without stops 10 miles long that can be driven in cruise control
    • Warm-up car for ~15 minutes say by practice, test drive the route
    • Bring car to test speed; reset trip meter, and; record 10 miles at given speed.
    • Repeat in opposite direction
    • Average the two and compare to the chart
    Bob Wilson
     
    #5 bwilson4web, Aug 9, 2016
  6. fuzzy1

    fuzzy1 Senior Member

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    #6 fuzzy1, Aug 9, 2016
  7. bisco

    bisco cookie crumbler

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    welcome kelly! did you just buy the car, or is this behavior new?
     
    #7 bisco, Aug 9, 2016
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