Help with poor city milage

The one thing that caught my eye was the use of "EV" mode. Don't use it for regular driving. At most, use it for moving in/out of garage for washing, etc. The engine has to run to replenish the battery anyway you look at it and it does it more efficiently during regular driving as opposed to idling..

 

I have noticed that going thru town at slower speeds (30 to 40 mph) has yielded the highest mileage. Stop and go lowers it quite a bit. The longer you are stopped, the lower your mileage. Sitting while waiting for a stop light is most likely going to be factored in as a 0 mpg.

 

Please answer the questions in this post:

http://priuschat.com/forums/gen-ii-...-answer-these-questions-esp-if-youre-new.html

The questionnaire helps people help you, by cutting out some of the initial back-and-forth.

PS: don't try to stay in EV. Remember that charge comes from the engine. If you're fighting to keep it near the right edge of the EV zone it'll be particularly inefficient.

 

As I recall, Tunica has mostly stop signs (no way to 'time' a stop sign) and some uncoordinated traffic signals on US-61. (no way to match the pattern)

It is small enough to drive anywhere and not warm up the engine. Dead flat.

25 MPH in town, 45 MPH on US-61 (I get my best 'in town mileage at 35 MPH, but 45 is better than 25, for me)

 

Never mind the distance between stop signs, what is your total trip distance per trip segment or engine warm-up cycle?

From a map it appears that Tunica and North Tunica combined are less than 2 miles end-to-end, not enough to fully warm the engine. If this is true, in-town MPG will be horrible in any car.

I figure that engine warmup costs me roughly the same fuel as driving about two miles with an already-warmed engine. If your trips are less than two miles (i.e. 4 miles worth of fuel), the only reason you are getting above half the EPA city rating, i.e. above 25 mpg, is that the engine is not fully warming.

 

I remember watching the warm-up phase in my Taurus. It was pointless turning on the heater until it was complete. You could clearly tell when it was complete. The engine RPM would suddenly drop. Just think what the MPG would have been during those first few minutes of driving. We were clueless back then... when automakers didn't include an efficiency gauge. Having such detailed information in Prius sure is an eye-opener.
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Stopping is wasted momentum, and it takes energy to build it back up. So the more you stop, the lower your mpg.

Completely inaccurate. Once the engine is warmed, it cycles off when not needed such as when waiting at a stop light. This is not 0miles per gallon it is undefined miles per gallon. 0miles/0gallons = undefined. Undefined on the Prius is 99.9mpg or 0.0l/100km depending on geographic region.

The exception is if you have a high drain on the HV battery while sitting there like high AC usage. Then you are lowering your mpg not now, but later when the engine kicks in to recharge.

+1

 

The OP still needs to answer the questionnaire.

 

Sitting at a stop light (with the Engine OFF) has no effect on mpg. Sitting with the engine on while warming-up does have an effect. Very short trips, like you do, will result in 30-35 mpg. This is still 15-20 mpg better than any other gas powered car.

 

General Guidelines

1) Set the 2010 Prius to "ECO" mode and not "EV" Avoid depending on the electric drive.

2) Your tires might not be Low Rolling Resistant tire(LRR). If you donot have LRR tires then you should consider replacing them with LRR tires.

3) Take your foot off the accelerator earlier before stopping so that the Prius will slows down and coast to under 14 mph before applying the brakes. This will likely require a lower top speed than you are achieving now. This is best done when there are few cars on the road or when you are in a multilane road that allows others to pass your vehicle if they get upset that you are driving too slow.

4) Redesign your commute trip/route to favor traffic lights over stop signs. Avoid both if you can. With traffic lights you can sometime synch yourself with the green lights and not have to stop - saving kinetic energy will increase your MPG - you cannot do this with a stop sign. In hypermiling this is called Driving without Brakes (DWB)

5) Avoid hard accelerations ( HSI in power bar) - when possible do gentle accelerations (HSI in ECO bar just under the "ECO" capsule). When possible synch accelerations on a downhill grade. Avoid accelerating as much as possible on uphill grades.

6) Speed and Fuel Efficiency go hand-in-hand. For city driving - the most fuel efficient speed range is from 25mph to 35 mph (75 to 65 mpg). For highway driving - the most fuel efficient speed rang is from 45mph to 55 mph (65 mpg). The Prius fuel efficiency declines as its speed increases from 60mph (56 mpg) to 75 mph (48 mpg).

7) The Prius mileage can be low for the first 30 minutes in driving (especially in stop and go driving, when the outside temperatures falls below 65F) because the Prius engine does not warm up as quickly to its optimum temperature. After the Prius is driven longer than 60 minutes/12 miles, its fuel efficiency increases and its is very easy to get over the EPA rating. There are four techniques use to increase FE (all are covered in Cleanmpg.com) by assisting the Prius ICE to achieve its optimum operating temperature:

A. Grill blocking (for the 3rd generation Prius is means blocking the lower grill air intake when the outside temps go lower than 60F).

B. Mini Warm up Pulse & Glide Cycles - at startup of a trip or route with a cold engine (ICE) you press the accelerator so that the HSI is always a little pass middle of the "ECO" bar but not pass the "ECO" capsule (this forces the ICE on and puts it into an fuel efficient 1.5KW operating range) and start accelerating until the Prius reaches its designated top speed of 10 mph - then you let go of the accelerator so that the HSI indicator is at the leftmost edge of the "ECO" bar but not in the "CHG" (regenerative recharging) bar so that the Prius is coasting via power created mostly by the ICE (and using very little electrical power). When the Prius speed begins to drop, you repeat this procedure over and over again but with a higher top speeds, e.g. 15mph to 20 mph for the second cycle, 25mph to 35 mph the third cycle, and soforth until the Prius is at its desired top speed. This avoids using the battery and accelerates warming up the ICE to its optimum temperature (coolant temperature = 180F). If you are in a traffic jam that is longer than 15 minutes - use this technique instead of using your electric motors to inch along in traffic to avoid draining your HV battery ( so the Prius can avoid needing to recharge it HV battery pack because of extended electric drive usage).

C. Install an engine block heater and heatup the engine before starting the prius. The ROI doesn't seem be significant unless you're driving in the Northern/colder regions like Canada, Minnesota, or Alaska. For Mississippi and Maryland - it's mainly for MPG bragging rights

D. Combine multiple smaller trips together such that any stop over does not allow the gasoline engine to cool down too much ( say less than 15 minutes per stop over). Hence, the fuel efficiency of each successive trip improves because it has the advantage/benefit of an engine that is already warmed up.


hope this helps

Walter Lee,
Cleanmpg.com "HyperDrive 1" mileage log
2010 Toyota Prius III, Blue Ribbon/Dark Grey, Oem Floormats
Yokohama Avid S33, 50psi/48psi
ScangaugeII (FWT, SoC, RPM, GPH)
100% grill blocking
Odeometer 17000 miles, 60.7 mpg overall

Best tank 727 miles/10.25gallons/70.9mpg
(calculated, summertime)
Worst tank 428 miles/08.18gallons/52.3mpg
(calculated, wintertime)

Best Commute Trip (16 miles, downhill, 70F degrees, 50/48 psi
tires, no rain/snow, no grill blocking, no AC/heat/defrost,
w/ warmed up engine) = 93 mpg (AVG ScangaugeII, 89 mpg PriusMFD).