Gas mileage - HELP!!! 38.3 MPG, what's wrong?

I never noticed a big different between ECO and NORMAL mode. So I drive the most often with NORMAL mode. I like this last because the car reacts more promptly than with ECO mode.
Best regards from Belgium.

 

This falls under the heading 'managing user expectations.' This chart gives an idea:

For most hybrids, there is a 'knee in the curve' between 40-45 MPG. In the case of our ZVW30 Prius, it seems a little higher, closer to 44 MPG. It doesn't mean a Prius getting less than 43 MPG is broken but rather we need to understand what is going:

• vehicle health - these are the mph vs MPG and hill-climb benchmarks for our ZVW30 on the drive from the dealer provide.
• environmental - there are ways to drive a Prius that drives the mileage down: short trips, high speed and A/C.
• behavior - leaving the car on over night (guilty), leaving the dogs in the car with A/C running (guilty), driving in "B" instead of "D" (guilty), accelerating to pass traffic going up a hill (no guilty, yet) . . .

Good mileage comes from the AND of these elements and one can often drive the MPG down. But sometimes, folks have to live with what they've got.

Bob Wilson

ps. About the chart:

The goal of the chart is to have the middle value of each set of vehicles lie on 100 point, X-axis value. The X-axis 0 will be the lowest for all vehicles and 200 the highest. Thus the X-axis resembles the IQ scale where 100 is normal. The Y-axis is the each vehicle's MPG.

I had noticed the average MPG for the NHW11, NHW20, ZVW30 and Insight fell between 45-50 MPG. But averages do not tell us anything about the distribution of mileage. We often learn more from the outliers than the averages.

Since the median MPG appeared to be ~47.5 MPG, I choose the inner rectangle to lie on 5 MPG boundaries that appeared to encompass the linear part of each line. As far as I'm concerned, anyone on the linear part is getting expected MPG.

The outer rectangle fits on the next 5 MPG boundary and identifies where there may be something going on that begs diagnosis. As for anyone outside of the outer rectangle, outliers, God and sparrows comes to mind . . . on both ends.

 

Bob, would you point us toward a good explanation of the x axis 100th value method of constructing a data axis? I see what it is doing and like the data presentation and might want to use it myself in the future. I am just not sure how you get there.

What are the two colored rectangles on the chart? They eyeball about right to be 1st and 2nd standard deviations, except they conveniently coincide with the 5mpg lines?

XS

 

Added a "ps" about the graph to the posting.

Bob Wilson

 

I just clocked 160 mi / 3 gallons for 56 MPG. Never gotten under 50 so far. 38fr/36rear.

something's way off for 38 MPG's.

 

PS stands for postscript. It means some writing that is added after the fact to an existing writing, initially it meant after the first writing had been signed, but it now seems to mean anything that is added after the initial writing.

The boxes are the way that prior posts are quoted in a reply post by the software used by this site.

 

I found the trick for analyzing Bob's charts: I squint my eyes, look at the chart, and go "Ooohhh, pretty colors!"

Tom

 

Wilson is probably going to kill me for commenting on this. But, hey, I am an engineer, and it took me a couple of shots to figure out what was going on!

For each kind of car, Bob figured out what the median was for the data set of reported gas mileages. Definition of median (most people here know, but what the heck): half of the reported MPG values for the (say) 2010 Prius are higher than the median; half of the reported values are less than the median.

Once he's got that, he divides each individual reported MPG value by the median, then multiplies by 100. That's the X-axis value; the Y axis value is the actual MPG for that sample. Plot everything for the 2010 Prius; then rinse, lather, repeat for all the other cars.

A particular report will be on the left side and high if a driver is a hypermiler in good standing; on the right side and low if a driver has a lead foot and wants to win the Indy 500. On the other hand, really low values might be due to something odd going on. 38.3 is on the low side, but we've had posters who (this one sticks in my mind) had their wives drive, and the wife got 10 MPG better.

Ha. YMMV.

KBeck.

 

Correct although I would add one bit of insight. If someone's mileage falls in the linear part, don't sweat it. A good part of mileage is the environment and typical usage. Some folks live in Prius-sweet times and places. Others live in Prius-hell. But if your mileage falls in the linear part, don't sweat it.

Bob Wilson

 

We took delivery on 31 July, both trip meters read in the 30 mpg range. It was delivered with a full tank (or so they claimed) and had 10 miles on the odometer. I immediately reset the Trip A display and it's been showing in the high 40's ever since. The Trip B, (Which I normally use to monitor miles between oil changes) still shows much lower than Trip A. I topped off the tank yesterday because gas prices dipped to $2.39 a gallon, reset Trip A, and it's showing mid 50's today. My suggestion is to just reset Trip A when you fill up and see what happens, I'm betting you'll see a marked improvement. I believe the dealer probably has these things sitting idling as they do the PMI, so that probably really skews the MPG reading.

 

Glad to hear that your expectations are closer to being met. It will get better as the car "breaks in". You'll see some great mileage in the Fall when the temps are cooler, but not cold.

Now the cold temps will be another thing entirely. Expect pretty awful mileage. If you can get an engine block heater (and have a place to plug in), this will alleviate some of the hit. There is also a thread on grill blocking, you'll want to take a look at that as well in preparation for the winter months.

Enjoy!

 

That's better than mine gets, it gets parked on the street. I don't know how cold your place gets in NY, but I heard that it does get a little chilly in New York in the winter time .

Typically, around Nov the posts start trickling in about lower MPG's and is there something wrong with my car. Happens every year. I was just trying to give you a heads up as to what will likely start happening in a few months time.

Your car will be fine.

 

Need? Nobody needs the EBH. Some people prefer the expense (both initial installation and the operating costs for electricity) to reduce winter's drop in fuel economy. Whether it's worth it or not is up to you; I'd probably just deal with it, myself. Of course, I'd probably be riding my bike and not driving, anyway.

 

To be a strongly competitive hypermiler, you need the heater all year round -- yes, even in the middle of summer, as sweltering summer heat is still far below engine operating temperature.

But for most drivers not competing for high MPG score or not living with very harsh winters, its value is not compelling.