EPA City Highway Vs Life

Discussion in 'Gen 3 Prius Fuel Economy' started by web1b, Oct 26, 2011.

  1. web1b

    web1b Active Member

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    According to the EPA, mileage is better in the city than the highway because it's a hybrid? Regenerative braking supposedly adding mpg?

    I have found this to be false. I get better mileage on the highway (50+) vs city (mid 40s or less). Lower city mpg just like any other car I've driven.
    What is with the EPA?
     
  2. mikewithaprius

    mikewithaprius New Member

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    Think of it like this: city (read: non-highway) driving has the potential for significant mileage increase versus the highway, since at non-highway speeds your car can basically shut off its engine and stop using fuel quite readily. Since there things like terrain, distance of trip, and a million other teeny things that can negatively influence city driving fuel economy, it just so happens it's not true in your case!
     
  3. Tideland Prius

    Tideland Prius Moderator of the North
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    It's probably because "city" is more like "suburban". I'm one of those who actually gets worse mileage on the highway.

    Your trips are probably just too short or you're doing too many of those and thus idling away and having to keep warming up the engine. I get 55mpg in the city and 47mpg on the highway (>60mph. At 60mph or less, I'm closer to 50mpg. 74mpg using SHM on a 50mph zone)
     
  4. xs650

    xs650 Senior Member

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    Their city cycle is about 11 miles long and takes over 30 minutes so the car is fully warmed up during most of the test.

    Most peoples city driving is shorter duration so they spend a higher percentage of their time driving with a cold engine.

    Edit: I noticed that Tideland beat me to it. Tideland, how long are you normal city trips?
     
  5. F8L

    F8L Protecting Habitat & AG Lands

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    Mike hit the nail on the head.

    On the highway, which makes up 95% of my commute, I can easily average 55mpg. Depending on the city, I can get even better mpg if I use pulse and glide or simply glide as much as possible. This really only works on streets with a lot of distance between traffic signals. For example, when driving in the city of Davis which has a lot of slow drivers and minimal traffic I can really boost my mpg. Conversely, if I have to drive in San Francisco my mpg will tank due to very frequent traffic signals, lots of rush traffic, lots of idling time, minimal ability to glide for long distances, etc.. It's just all depends on the city.

    I also notice that in some areas the highway appears to kill mpg in both directions! I know of 2 sections that appear flat but my mpg drops like I am going uphill but it happens going the other direction as well. I blame Obama, I mean Dick Cheney or..... lol
     
  6. fuzzy1

    fuzzy1 Senior Member

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    I, however, have found it to be true -- mid 50s on the highway, mid 60s on my 18 mile (one way) commute, when taking the all-city route (45 mph max, 35 mph typical, with significant portions at 25 and 30). And in the best weather conditions (July-September here), it beats 70 mpg on that commute, much more often than it beats 60 on the highway.
    They didn't ask for your specific 21st century city conditions, they just took a hypothetical average of typical early-1970s driving.

    People complained about the numbers being unrealistic. EPA discounted the numbers. People drove faster and harder, because the new more powerful engines made it possible. People complained about the numbers being unrealistic, again. EPA discounted the numbers, again. People drove faster ...

    Rinse and repeat.

    Note also that EPA labels are marked down from the actual test results, and the highway numbers are marked down a larger percentage than the city numbers. Because of that, many drivers will have to work harder to match the City rating than the Highway rating.

    Now go read the articles to which Cwerdna points.
     
  7. walter Lee

    walter Lee Hypermiling Padawan

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    I get better city than highway most of the time but I'm hypermiling. The city advantage is that wind resistance is very low and the power requirements are low so the Prius ICE is not running all the time (which saves gas). The city disadvantage is that if the ICE is off for too long then it loses heat (this occurs most often in the winter) and it starts up again to keep the catalytic converter warm. In addition, when the Prius is stuck at very low speeds for longer than 20 minutes it tends to drain the HV battery and when the HV battery state of Charge (SoC) drops below 45% and the accelerator is press too hard then the Prius will activate the ICE to aggressively recharge the HV battery and its MPGs will drop. To avoid this scenario, I do a low speed Pulse and Glide when the Prius is stuck in urban bumper to bumper traffic = this is done by briefly pulsing/accelerating so the HSI passes the half way marker slightly passing the ECO capsule marker until the Prius hits 10-20 mph then releasing the accelerator so that the HSI is at the far left end of the ECO bar but not in the CHG bar. This puts the Prius in glide cycle/mode where its mainly travelling forward on its own moment until you apply the regen brakes and stop. To minimized the use of the ICE, the starting *glide* top speed is set so that rolling resistance/gravitational forces gradually slows down the Prius to about 5-12 mph - about one car length before the regenerative brakes are applied to stop. This technique also heats up the coolants slightly too. This technique can help prevents the HV battery from draining below 45% when the Prius is stuck in bumper to bumper traffic for over 20 minutes...

    The highway advantage is that the engine at its most efficient temperature (170F to 190F) . One can actually drive very efficiently by allowing your highway speed vary from 65mph(downhill) to 55mph(uphill) uses a hypermiling technique Driving with Load (DWL) but I found it was difficult to do for longer than an hour or two. This year on my annual trip from DC to Detroit using non highway road going westbound from DC to Detroit the Prius got only about 55 mpg, but on the return eastbound superhighway trip with the cruise control set mostly at 55 mph (using the Ohio Turnpike/PA Turnpike/MD Interstate 80/76) I was able to achieve about 63 mpg! In both directions the Prius was using E10 87 octane gasoline, the tire pressure was set at 44psi/42psi, outside temperature was 70F, there was no grill blocking, distance travel was about the same 550 miles, but the travel time for the highway was shorter than the non-highway route by over an hour. In 2009 and 2008, I travelled this same superhighway route with a Gen2 Prius going slightly faster (60mph avg) I was able to get 55 mpg.

    One of the most important factor in going this slower on a super highway is that the trip has to be timed so there is less traffic on the super highway so the Prius can travel at these lower highway speeds safely - I found for this superhighway route the best time are Tuesday to Thursday ( Weekend traffic on the Turnpike can be extremely heavy for some reason).

    hope this helps

    Walter Lee
    2010 Toyota Prius 3 (Cleanmpg.com "HyperDrive 1"),
    Ribbon Blue/Dk Grey, oem floormats,
    Yokohama Avid S33(50/48),
    100% grill blocking,
    ScangaugeII(FwT, SoC, RPM, GPH),
    Odeometer=+16500 miles, 60.5mpg overall
    last tank 692 miles/10.24 gallons = 67mpg (10/22/2011)
     
  8. Tideland Prius

    Tideland Prius Moderator of the North
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    My commute is 9km long each way, just enough for the 3rd Gen to shut off its engine up to -10°C (in the 2nd Gen, that'll be enough only in the summer months because the previous 15km route was barely enough to warm the engine at 0°C). Short trips kill my mileage big time. If I do a coffee run a few times over the course of a tank, I'll be closer to 50mpg. Our 2005 is now averaging below 50mpg because of the short trips and the elimination of the longer 15km trip (it's now 7km) so the balance is gone and mileage tanks.
     
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