Poor Fuel mileage - typical?

Discussion in 'Gen 3 Prius Main Forum' started by Suzanne Betts, Feb 5, 2018.

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  1. Suzanne Betts

    Suzanne Betts Junior Member

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    Hello everyone. I've read other threads, so I apologize if this is a repeat. I purchased a used 2012 Prius with 98,000 miles on it about 6 weeks ago and have had three fillups since then (which is the relatively nice part, fewer fills). However, when I rate the mpg it seems to be 34.5 to 42mpg, approx, based on the fuel and miles driven for that tank of gas (iow, actual). The car says I'm doing better than that for mpg, and I've seen in other posts that the car estimate and actual mpg don't match. But would you expect that the car needs servicing in some way that would help the mpg to be better, or is this what I should regularly expect? I've also tried to drive according to the recommendations to extend my fuel efficiency. And lastly, I just checked the tire air pressure, and they were at 35 so I filled to 50 - that might help me see a little mpg difference on the next fill. Other ideas? I just wonder if there is something in the car that needs tune-up or repair that would affect this more clearly. It seems to run fine, although I've occasionally noticed a tiny little jerk when it shifts itself....thanks!
     
  2. David Beale

    David Beale Senior Member

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    Welcome to Prius Chat Suzanne.

    Drop the tires to 40 PSI for safety. Usually you run the fronts 2 PSI higher than the rear. I run 40 front and 38 rear in summer and 2 PSI higher in winter all round.

    Your mileage is about "normal", if mileage could ever be "normalized". It takes a lot of effort to get better mileage, especially in winter, even though it's not cold where you are. Some come by it naturally and will tell you it's easy. It isn't for others.

    You could try having the engine air filter changed. A dirty one can effect mileage and it's a relatively inexpensive fix. If you were in last summers fire areas/smoke both it and the cabin filter should probably be changed.

    The 3rd gen Prius tends to estimate higher mileage than you actually get so that is normal.
     
  3. bisco

    bisco cookie crumbler

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    congrats and welcome!

    the first thing you should do is search for maintenance history to make sure the car has been properly serviced. you can sign up at toot owners and enter your vin.
    although there is nothing major until 120k, you should check the air and cabin filters, 12 volt battery health and oil level.

    a major player in mpg's is tire brand and model. since you are at 100k, someone might have installed cheap high rolling resistance tires.
    lastly, trip type, driving style, weather, seasonal gas and topography all affect mpg's, and the margin between 30 mpg and 60 mpg can often be attributable to all these factors.

    there is no such thing as a tune up in a prius, but there are items not mentioned in the maintenance manual that can be looked into, once you have checked all the low hanging fruit.
    all the best!(y)
     
  4. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Those are three calculated tanks then, and that's the range? Was the latest tank the 42 mpg? The low one, if the first, could be due to vagaries of the fillup when you got the car. I would give it a few more tanks, just to see where the numbers stabilize. It's good btw, that you're calculating, the display is fairly rose-tinted.

    I'd chime in, bring your tire pressures down some, 50 is bone-jarring, might be reducing traction/grip, though I'm not sure. Try somewhere between 38~42? I set ours all to the same value, not sure of the import, Toyota's instruction to have a few more pounds in the front.

    Again chiming in: it could be tires with high rolling resistance. Can you check what they are, make/model, and post? The more complete the description the better. Often posters will say "they're Michelin, or Goodyear", which doesn't really nail it, lol.

    Air filters, engine and cabin, are worthwhile to check, if only to get a sense of of the car's condition/history. If the engine filter is only slightly dirty, I would not have high expectations that a new filter will improve mpg. It might actually drop it slightly. Cars are computerized, monitor air flow and tailor fuel injection accordingly. A slightly dust filter might actually give better fuel economy, sort of reducing the engine size, if that makes any sense. Anyway, doesn't hurt to check them.

    Judging from the time you've had the car and number of fillups, you're likely not doing a lot of short trips? That's one thing that's hard on miles. Also good to consolidate trips.

    The "jerk when it shifts itself" could be nothing, or something in the transaxle. Maybe check it's history, see if the transaxle fluid has been changed. If it's not possible to ascertain, or just to be sure, wouldn't hurt to get it changed. It's NOT on the Toyota proscribed maintenance, but dead simple. Done professionally it shouldn't cost over $100. 4 quarts of Toyota ATF WS fluid is more than sufficient. You simply drain the old fluid, reinstall drain bolt, add new fluid through the fill bolt (with the car level), and the level is right when it starts overflowing. I'll attach a Repair Manual Instruction. This is basically a preventative maintenance, won't "cure" an underlying issue, if there is one, but doesn't hurt.

    Check the engine oil level on the dipstick, make sure it's between the marks, preferably near the top mark. Was the oil changed recently? For easiest checking: remove and wip the dipstick, and wait say 5 minutes before reinserting for the check. The Prius dipstick tube is prone to draw up oil when the dipstick is removed, and waiting gives it a chance to drain down.

    There could be an issue with brake drag, and this is something that could definitely lower mpg. The rear brakes in particular are prone to disassembly after maintenance, in a way that causes uneven wear and extra drag. Feel all wheels immediately after a drive, see if any feel hot, this would be a tip off. Also, with the rear off the ground and parking brake off, definitive check would be to spin the rear wheels. There's a slight amount of drag inherent with the rear disc brakes, but it should be minor: the wheels should easily spin one or two revolutions.
     
  5. fuzzy1

    fuzzy1 Senior Member

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  6. Sam Spade

    Sam Spade Senior Member

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    The first thing that SHE should do is drop the tire pressure back down to something under the maximum safe setting which is shown on the tire sidewall; probably 40.

    Then one should not take a wild swing at things that you really don't understand......like maximum tire pressures.

    And of course there IS such a thing as a tuneup with a Prius.
    Plugs, throttle body cleaning and EGR service comes to mind.

    And the first thing YOU should do is change that ridiculous signature that you have.

    But I think the numbers are well within a "normal" range, especially in the winter.
    To get a good feel for the actual mileage, the calculation should be made over several fills and several weeks......minimum.
    Calculating each tank fill is often inaccurate.
     
  7. Johnny Cakes

    Johnny Cakes Senior Member

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    I just passed the one year mark with the 2014 that I purchased used. I was expecting 50+ MPG right out of the box, so I understand your concern.

    For highway mileage, a very normal and HUGE factor not yet mentioned is speed. There are charts in various threads on PriusChat showing a pretty steep curve and direct correlation between higher speed and lower mileage. I came to learn that the 37-40 MPG I was getting was perfectly normal for the highway speed I drive. For me, the time savings is worth the extra fuel cost, although with gas prices rising 12.5% over the past year, that may not always be true in the future.
     
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  8. Andyprius1

    Andyprius1 Senior Member

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    If you are doing 65+ mph, you will not get great mpg in Winter, do you always take your foot OFF the gas pedal on downhill rolls? Do you race up hills? Do you turn off, or down, the heater, defroster? The really efficient heater is the seat heater, use that as much as you like. Remember speed is the greatest inhibitor of excellent mpg. Definitely clean the air throat and sensor, with 98000 milesl
    that’s overdue.
     
  9. Grit

    Grit Senior Member

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    Is Nevada City a very hilly mountain city? That could cause your mpg to go down quick.
     
  10. MelonPrius

    MelonPrius Active Member

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    Suzanne, what year/make/model did you drive prior to the Prius and what was your average mpg on a tank in the winter?

    A good test would be taking a long highway trip with the cruise control set at 70 mph or lower. Set the tripometer after the engine is warmed up and stop it after getting off the highway (100 miles or more). You should get over 50 mpg on the car's tripometer for the trip. If you do, then driving habits and conditions will play a big factor for your lower mpg.
     
  11. B. Roberts

    B. Roberts Hypah Milah! Ayuh.

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    Tire brand/inflation, air filter, engine oil type, load in car, outside air temperature (OAT), hills, winds, aggressive acceleration, high speed travel, snow, rain... the long list of things that can affect MPGs. Hopefully your Prius wears low rolling resistance tires, uses the proper weight ( 0W20 ) high quality synthetic oil, a clean engine air filter with a clear intake plenum, and using a top tier gasoline brand. At 98,000 miles, new spark plugs and wires could help, too.
     
    #11 B. Roberts, Feb 6, 2018
    Last edited: Feb 6, 2018
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  12. Suzanne Betts

    Suzanne Betts Junior Member

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    Hi everyone! Thanks for the warm welcome. Sorry I didn't answer sooner - hit a busy week. So to answer some questions you all asked:

    My trips are generally short, even very short at less than one mile to work and then home. From what I've read (am I right) - this car should get great mileage at shorter trips at lower speeds (I'm at about 15-22mph on these trips). It's the longer faster trips that reduce mpg from using the ICE. About 2-3 times in a tank of gas I "go to town", which is 20 miles and at 45-55mph. However, as someone pointed out, I live in a very hilly area in the Sierra Nevada Foothills, to going to town means down into the Yuba River Canyon and back up the other side, a drop of 1000' in a few miles. Yes, it's quite hilly here and it could be most of my tanks of gas are under these conditions.

    I try to drive un-aggressively, and coast down those long steep hills (dash says 100+mpg). Hey - does it help recharge the battery if I switch to the B mode while going down those big hills? It creates such a huge drag that literally I have to either keep shifting from B to D, or add gas sometimes. And it's a big hill! I haven't found the B to be all that helpful, but I'd love more feedback on that and gas mileage.

    TIRES! Ok, they are here because I looked them up and found them at simpletire website online. You all would know what all this tire stuff means better than I, but the side of the tire actually says the max fill is 51 PSI. That's why I filled to 50. I can drop them if you recommend it for safely, and I think I am not so sensitive to notice if they cause a more bumpy ride being filled that high. They are fairly new tires, probably changed at the dealership before I bought it. So they will be on the car for a while. They are Doral SDL 65A 195/65R15 91H tires, tread/traction/temp 400AA. Maybe you have additional suggestions or comments on tires?

    Looking at the carfax report I got when buying it - oil and filter were changed about 1000 miles ago, which occurred on 9/14/17. Do I change it again, even though the miles are so few since that last change? It also says safety and emission inspections were made on that date at the dealership.

    At 82,200 miles it had engine/powertrain computer and module reprogrammed. This might be standard maintenance for this 2012 Prius?

    The only other event of any consequence on the Carfax is at 23,400 miles when the maintenance and inspection was completed. So no mention anywhere of changing transaxle fluid or anything else very useful.

    Well, I'm hearing from all the various comments that I should change cabin and engine air filters because there is no knowing when that happened last, have the 12V battery health checked, check oil level, and possibly change transaxle fluid as well as spark plugs. Am I on the right track?

    You all are awesome. Thanks so much for your kind help.
     
  13. Prodigyplace

    Prodigyplace Senior Member

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    Trips of 3+ miles at low speeds get great mileage. For a 1 mile or less trip the engine will not be able to complete its warmup cycle, hurting mileage. These short trips may e what is hurting your mileage.
    The Prius is designed primarily to be a low emissions, efficient vehicle. The engine, once started works to get to its most efficient operating temperature as quick as possible. The great mileage of the Prius is really a secondary goal as part of efficiency,
     
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  14. Sam Spade

    Sam Spade Senior Member

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    This. The 3+ miles figure might be debatable; I think it might be a bit higher. Unless maybe it takes you 20 minutes to go that 3 miles. ;)
     
  15. MelonPrius

    MelonPrius Active Member

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    Before these trips, set either trip A or trip B to 0 and record the mpg for a round trip. Again, use cruise control if possible as it helps to take the human lead foot out of the equation. You should average well over 50 mpg for these trips, depending on the number of lights and if the engine is warmed up. Even if you don't track it with your tripometer, the dash will display your mpg for each leg of your trip after you turn off the engine.

    I asked about the mpg for your previous vehicle because many people that will average below EPA estimates for their previous vehicle will also do so with the Prius. But since the Prius starts at a much higher number, the over mpg will still be improved.
     
  16. BZzap!

    BZzap! Senior Member

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    Prodigy place is spot on with his/ her observations.
    A one mile trip is probably less than is needed to get the ICE into closed loop operation. The car is in a warm up cycle most of that time, if not completely. The same thing happens on the return trip. One can not expect fuel consumption to hold up to manufacturers estimates under those conditions. It just ain’t gonna happen.
     
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  17. MelonPrius

    MelonPrius Active Member

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    Yep, and this would have been the case with her previous ICE cars, too. IMO, the plug in Prius would have been a good choice.
     
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  18. Grit

    Grit Senior Member

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    I'm from that county and know those hills. Those hills will kill your mpg efficiency. Don't do the cruise control test for 30 mins there either to get a consistent mpg reading, engine will rev too high. To get a better measurement, the next trip to Roseville or Folsom, reset trip a or b mile reading and drive around those town for a much more accurate reading of mpg.
     
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  19. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Plugs yes, wires no: there are individual ignition coils at each spark plug, and just a regular wiring harness to each.
     
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  20. bisco

    bisco cookie crumbler

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    suzanne, it sounds like you have hit the perfect storm for bad mpg's.

    sounds like you are on the right track, but the tires may be a problem, no way to know how many mpg's they are costing you.
    short trips are a killer as pp mentions above. not much you can do about a commute, but if you can string together other short trips, that will be helpful.
    the good news is that short trips hurt non prius even more.
     
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