2005 Prius at 65 mph, MPG?

Bob Wilson used to have MPG graphs for Gen 2 and Gen 3, (which I can't find) they were very close at 65

here is his Gen 3 mileage notice that 65 is dip.

 

I can't speak for a 2005, but have some comments that will apply to any Prius.

"Almost flat". How much elevation change from between the start and end points? Even 150 feet of descent over that distance is worth roughly a 1 mpg boost.

High tire pressure helps, many of us run in the 40s. A very few hypermilers on a different forum run much higher. Note also any odd tire size, as a slightly small tire will significantly boost apparent mpg, even thought the real number is unchanged. This is a double whammy, from both speed error and distance error. Worn tires will also read higher, both from easier flexing and from smaller tread diameter.

How was fuel measured? The 2005 has a fuel bladder that has notoriously inconsistent refill behavior, enough that many consecutive full tanks need to be added together to get accurate mpg numbers. The built in mpg gauge on the dashboard is much more accurate for shorter trips.

Pure gas, or E10 ethanol? This ought to make a 3% difference.

Cold start, or was the car pre-warmed? This probably makes a 2 mpg difference over an hour trip.

I'm sure there are plenty more things to watch.

Was there any tailwind? Even a small breeze will help.

 

How are you measuring 1.06 or 0.9 gallons? If you're doing what I guess you're doing, the fill was too short/small and there's a huge margin of error.

As for the Gen 3 case, why are you surprised?

Were the trips made going in both directions over the same route, to help cancel out the effects of elevation change and wind?

 

I doubt that whatever device it is makes any difference when it comes to FE.

As for huge margin of error, even on much larger fills, I and others on the Gen 2 can find the manual mpg calculations are way higher than the MFD (multifunction display) on one tank and much lower on the next, even on "fills" of 6+ gallons each, partly due to the bladder, guess gauge and complex fuel tank assembly. To do fills of only ~1 gallon really means a huge margin of error. Unless you're going to install something in the fuel system to measure usage/flow, you're better off trusting the MFD in the Gen 2. It's pretty accurate.

The Gen 3's trip computer supposedly reads a bit high, so you'll likely need to take off a few mpg.

You might find these insightful: http://priuschat.com/forums/other-c...uth-about-epa-city-highway-mpg-estimates.html and http://priuschat.com/forums/other-cars/94001-gas-gauge-says-full-but-thats-not-quite-true-npr.html.

Unfortunately, the EPA ratings on Compare Cars Side-by-Side for the 2nd gen were most likely obtained by adjusting the pre-MY 08 EPA numbers via formula vs. running the new test procedure (w/3 extra tests) that the Gen 3 most likely went thru. We may never know the numbers the Gen 2 achieves on the newer tests.

Most fuel-efficient cars is what CR got in their testing on Gen 3. http://web.archive.org/web/20081231...-advice/most-fuelefficient-cars-206/index.htm is for Gen 2. Last page of http://www.consumersunion.org/Oct_CR_Fuel_Economy.pdf describes their method, sorta.

 

You seem to be pretty "hush hush" on the nature of the device. Is it a secret? Are they trying to get you to invest in it?

 

We haven't established that at all. It is completely possible that they did show you something worth remembering.

The problem is that this is still within simple spin range, should they choose something less than full disclosure and honesty or are not fully informed about what is possible without magic devices. It is up to them to demonstrate that this is showing a real improvement from their magic device, and they have not yet done so.

Question: At what elevation was this test? Higher elevations will produce better results, though hybrids benefit by a smaller fraction than do non-hybrids. (All cars face less air drag in the thinner air of high elevation. Non-hybrids also get some part-throttle engine efficiency improvements, while most hybrids already get even more of the same thing independent of altitude.)

Suggestion: Next time, take a GPS to crosscheck both the speedometer and the trip meter. If the promoters are being honest, the speedo should be lying by 1-2 mph (this is an industry norm and a legal requirement in some areas), while the odo should be accurate to a fraction of a percent. If the car's measurements are more optimistic than that, somebody has fudged something, such as the tires.

 

I just purchased a 2007 with 71k and my first fill up today was 9.1gal. The mfd showed 46.5mpg and my actual calculations: 483miles divided by 9.1 gave me 53.07mpg. The fuel gauge had just changed to one square left, thats when I decided to get fuel. I still had 1.8gal left in the tank. Not bad for a first fill up. It should do better when it gets warmer out. I usually never drive faster than 60mph. At 65 noticed a big drop in mpg. Great forum.

 

How do you know you still had 1.8 gallons left in the tank?

You do realize that you have a bladder-style fuel tank so the actual capacity changes with temperature right? The capacity is not always 11.9 gallons and in some cars it may never be.

Please spend some time doing searches on the topic of gas tank capacity. You'll quickly find out why it is not a good idea to try and rationalize how much fuel you have left and just "listen" to the car when it tells you to add fuel. The best way to avoid running out of fuel is to fill up when the gauge reaches two pips (bars). I'd hate to hear you ran out of fuel in a dangerous area.

 

The gas tank is larger when it is warm, and smaller when it is cold.

So I have pumped over 11 gallons in summer but often can't fill it over 9 gallons in winter. Even morning to afternoon is a different size tank. Be very careful making any assumption about gas you have left. I have run out, if you play below one pip, you will too, just a matter of when.
Alone with no one to strand, I get gas at one pip.
With years of time to hear about it, I get gas at two pips when my wife is in the car.
With your mother in law in car, get gas at three pips.

 

Definitely "sage" advice. LOL