Prius MPG Test!

I thought this was very interesting, to see the real numbers.

Although I am still waiting for my Prius but around here most of my driving will consist of about 8 miles of city and 25 miles of freeway per day with averages on the freeway of about 60 (65 mph speed limit 55 trucks and construction, all the time). I will however take some trips that take me from 65 to 70-75mph limits/driving. I wondered how these speeds would impact the mileage but it doesnt seem so bad.

My parents just made the trip I will make from time to time of about 900 miles each way and limits from 65-75 and they averaged about 45 mpg on a brand new prius on the way down (ohio to northern florida). I am impressed with this and happy to see your results are similar to what I was hoping for. Now if I can only get my gas guzler sold soon so I am ready for my new Prius...

Thanks for the info Wayne

 

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Interesting results.. I've tried the same before for myself on the way home from work (12am-ish), with not much cars around, and I've found strange results with mine where sometimes I got better MPG at > 121Km/h than at 118Km/h or lower. It may have been the terrain, but it's difficult to find a nice predictable track of freeway to run around in SoCal.

 

Thanks for taking the time to make these careful measurements!

I would have expected fuel use to scale with the kinetic energy of air displaced, at least at the high velocity end. Therefore it's of interest to re-plot your data as fuel used as a function of velocity squared. Excluding the 55 mph data, the fit is OK...[attachmentid=693]

 

Results look pretty reasonable for my car at around 80 degrees, except for some reason I get less at 55 mph. I don't see temperature listed, but the effect is big.

My general rule is 55 in winter = mpg of 70 in summer, this from reading someones graph posted a year or so ago. Foget what temps I looked at but I think I figured summer at 80 degrees and winter at 10 or so.

I also notice a jump up in mpg when it rains light so the air is humid but roads aren't wet enough to add drag.

 

Very nice data. I only get up to highway speeds occasionally, but I am driving a bit slower now. The limiting rate is making people around me crazy!

 

Wayne, this is good information, I'm glad you took the time to do this. I actually was hoping it would show no great penalty for speed because sometimes I drive to fast, but I'm not surprised at the results. I ordered a spoiler from Brian at BT Tech and plan on doing some before and after milage tests when it gets here.

 

Cool stuff. I'm going to give it a try too at temps from 80 down to 30 degrees and compare my data. Also, thanks for the spreadsheet.

 

Thanks.

Your car is about 2 mpg better than mine at most speeds. Hope mine is still breaking in.

 

Thanks for sharing. Very interesting indeed!

 

I see that you discussed the milage difference with a/c on and off. Were the windows opened when the a/c was not in use. I am wondering if the c/d changes the mileage with the windows open at highway speeds. I notice some buffeting with windows open at highway speeds and would imagine that it dirties the c/d which would lower the mileage.

But does it lower it more or less than the a/c does?

 

c/d= coefficient of drag. Woudl be interesting to know the difference windows up vs. windows down. It could make a compelling argument to use a/c and keep the windows up.

 

what i'd love to see is something like this that goes down a bit more - i'd like to see 45 and 50. i'm blessed with a regular route with speed limits of 40 and 45mph, and would like to know what i can expect with my new prius. we who don't have them yet have to live through you!

 

You get better mileage at 70 mph than we get at any speed.

I have not attempted to measure as precisely as you have, but just based on what the
instrumentation shows at various speeds, our chart would look more like this:

MPH MPG change difference from your results
55 45 +3 +7% -18 -30%
65 44 +3 +5% -11 -20%
70 42 ref ref -8 -16%
75 40 -2 -5% -6 -15%
80 36 -6 -15% -2 -6%

Tires at 41/40, temps around 65. No A/C or heat.
2005 Prius II with about 5K miles on it. Built about a month before yours.
Gas here contains 10% ethanol.

 

Where is here?

 

Here is California, where they make up for giving us lousy gas by charging us an extra 50 cents a gallon for it. :wacko:

Since our summer gas is already oxygenated like everyone else's winter gas,
what do they do to our gas in the winter? add water?

Yes, it all claims to be 87 octane.