MPG as a Function of Highway Speed

You'll do better on dry pavement, I bet. Rain and snow can add to the drag.

 

Oh yes. I have lost at least 5 MPG in the snow. (plus more losses for temperature)

 

Absolutely. It is quite noticeable even in my non-hybrid, where the nonlinear nature of the MPG scale makes it much less visible.

 

Not around here (Central Maine). This is my 6th winter since my move to Maine and I think I'd rank it number 3 for mildness. We've had one week with very cold days but mostly it's been relatively mild, with plenty of high 20s and snow-busting flashes of warmth and rain that have left a lot of ground clear of snow much of the time until the heavier snow of the past couple of weeks.

The mpg seems low, but you didn't say what the temperature was at the time.

I haven't found much economy loss in snow, but I'm still on my regular Fuel Maxes and have the pressure up. Ironically they seem better in snow than rain.

The extra tread of snow tires hurts mpg and definitely get those off quickly when spring comes. Snow tires are soft rubber for extra cold grip, so as temperatures rise they become excessively sticky.

 

In the midcoast, according to Heating Degree Days, I have the following (so this year is moderate as far as temperature goes (number does NOT include February, and the percentage is pro-rated) :

Season

2004-2005 7,950 108%
2005-2006 7,173 98%
2006-2007 7,437 101%
2007-2008 7,393 101%
2008-2009 7,903 107%
2009-2010 7,028 96%
2010-2011 7,599 103%
2011-2012 6,551 89%
2012-2013 3,883 95%

 

My fill-ups are down about 7 mpg (from the 58 that I was averaging last summer).
Conventional wisdom is that the snow is bogging you down, snow tires are too and the temperatures are too. My 7 mpg penalty is almost entirely temperature related. I'm running the OEM Yokohama S33D tires and not dealing with much wet or snow. I also don't do any high speed freeway driving to speak of.

 

Interesting. 2009-2010 and 2011-2012 were very obviously mild for us, I particularly remember that 2009-2010 we were weirdly North of the bad weather with Southern Maine and other parts of New England getting slammed at times.

We have another relatively warm week forecast, so I can't see that 95% changing too much.

 

Never mind the seasonal snow, rain, cold or whatever else.

Aerodynamic drag is ALWAYS there. It's a big point with me....the faster you go, the lower the mileage.

Slow down, up the mileage....really simple.

 

The peak appears to be about 42 mph for me. And in my part of California during rush hour, 55 mph is optimistic for highway speed. I can average about 60 mpg at that speed. I don't think it's a coincidence that the center bar on the HSI is exactly where I get optimum fuel economy.

 

Yep, the cold weather, snow and snow tires is badly hurting mileage. More info at Why mileage gets worse in winter | PriusChat

Bob Wilson plotted Updated MPG vs MPH chart | PriusChat long ago. Not sure if he's got a newer version. ZVW30 is the Gen 3 non-plugin Prius. CR got 55 mpg on their highway test. Results at The Most Fuel-Efficient Cars | Best Cars for Gas - Consumer Reports. Per last page of http://www.consumersunion.org/Oct_CR_Fuel_Economy.pdf, their highway test is run at 65 mph.

Given that the PiP is actually rated at 1 mpg higher on the EPA highway test (Compare Side-by-Side) than the non-PiP, I doubt the PiP would do any worse on the highway. If you wish to learn more about the EPA tests, read the links at Car and Driver: The Truth About EPA City / Highway MPG Estimates | PriusChat.

You can also determine net elevation get/loss via Google Earth can give you an elevation profile of a route between 2 points! | PriusChat.

 

I drive on the freeway every day to work and go 50 to 55 in the right lane...I have had only one person flash there lights behind me in a month. They are not paying my gas bill, so who cares if they get mad. I find that most people expect to pass a prius anyway. I just filled up my 2nd tank if gas and got 1044 miles to the tank and 122 mpg. Slow down and you will reap the rewards.

 

+1
I can take two different routes to/from work/home..
1) Long Island Expressway- three lane expressway. Must maintain 65mph minimum to prevent getting run off the road by 18 wheelers, SUV's, pickup trucks, BMW's on their way out to The Hamptons, etc... I average 73-88mpg on my 56mi (round trip) commute.
2) Rt 25a- two lane local road. Almost same distance as the expressway to/from work, top speed may approach 45mph, but never exceeds 50mph. When I take this route I can get up to 120mpg with the PIP.

Speed kills mpg.

 

I routinely drive between 55 and 80 on the highway between my house and work. ~55 miles highway and 14 miles side roads. I was getting 60+mpg before the winter and have been getting ~50-55 for my entire trip. It is also in New England and very hilly. With Cruise Control I get a lot of coasting time or with traffic I gently slow down as carefully and slowly as possible.

AFAIK the Prius uses a continually variable transmission so that will have some impact to how gas mileage goes at various speeds.

 

The Power Split Device in the Prius is not really a continuously variable transmission (the gear ratio is fixed), but the two motor-generators and the software together simulate the effect of a CVT.