Colder weather has zapped my mileage to 44mpg

Data collection is fine. Spinning it to the point of garbage is not. Indy has decided that cold weather affects Prius out of all proportion to other cars, and cherry picks data to support his opinion.

Anyway, another data point from my 100 mile drives in the high desert winter of New Mexico: Round trip of 100 miles * 2 legs starting from a cold engine each time, speed average about 60 mph, temps in the low to high 20's F: 56 mpg by MFD.

Works out to be about a 6.6% hit on mpg compared to nice summer results.

 

on the subject of data collection. this is one of the most important aspects of this site. observations by actual owners!!

now, if the data is presented with opinions, ok. what is wrong with that?? its not that tough to collect data. only takes a little teeny weeny bit of discipline really...nothing more.

now, being able to analyze that... well, ask Galaxee or any other person involved in that kind of work. a collection of data can be subject to many different interpretations all of which is going to be clouded by personal experiences of each one of us here.

a truly scientific analysis without a strictly controlled environment is not possible. so additional observations by the data collector are required. things like, "i was late, so drove faster one day" or this tank included trips not normally taken, etc"

now, even repeatable trips still have a lot of variance.

i collected data nearly daily for my work commute. (i posted it here) and it have more than a 30% variance. and why is that?? because on an open road with other traffic, you cant do the same thing everyday... you might think those little changes dont make a difference, but they do. and there is very little you can do to quantify those changes without recording observations over an extended period of time.

 

All the up and down was two lane highway. My average speed was 34 mph - slightly up from my usual of 30-32 with a mix of residential and moderate traffic highway driving.

 

Actually, multi-variate regression analyses against controls, and with N large enough to tame random variation and unmeasured confounding variables is the way to go

Opinions about data interp are like other opinions: Everybody has a right to their own, and can express them. But No one should expect others to take them seriously, or even listen, if they are poorly thought out nonsense.

 

well said and i also take everything i read with a grain of salt...after all, i post a lot of stats here and turnabout is fair play !!

 

Attached the screenshot of my MID after a 706km/439mi trip, from Florence to Munich (check maps for terrain details - it is not flat!), average speed of 94km/h-58mph and average consumption of 5.5km/l-43mpg (add 5% for real value) - the weather was always with temperatures below 0C/32F, often around -5C/23F or lower (especially in Austria).
If this is how cold is zapping my consumption, with that speed average on EU highways with often 130km/h-80mph speed limit, I am pretty happy with it. I could not manage that with my 1.4L TDI Polo, ever. I was more around 6,5L/100km-36mpg.
No grill blocking. 2-2500km old 195/55 R16 winter tyres at 2,5/2,3 bar - 36/33 (if I remember correctly - but they were pumped the day before). Heater at 20C/68F and either normal or Pwr mode (mostly the former).

 

Enough is enough Sage! Please leave me alone. Read the last post by Alfon. Also said that that the prius winter mpg drop is unprecedented from everything he drove since 1960! Others have said it too! So, please do ignore me and let's focus on making the discussion productive and interesting! I beg you!

 

By the way... I will keep posting what I'm getting with my trips. I do believe these trips are long and steable enough to build a nice set of data. I know some folks here do appreciate the data regardless of my interpretations. I had the grill blocked in my last one, under 20F and the speed was slow, around 55 Mph (don't have the data here with me for exact numbers) and Mpg was only around. 41-42 calculated. I have to compare it with other trips in similar conditions but I don't think the block helped a lot. Anyway, there was light snow for about 40% of the trip, so that was a negative factor too, of course. Later I will post the exact numbers and photos of the mid and grille blocked as asked before...

Cheers...

 

This is the first real winter test for the 2010 Prius.

Posting about how your Prius is performing during the winter is good info for all of us. Even if you don't like the results that a Prius Chat member reports, facts are facts.

Lets face it people in the U.S. live in all different climates and terrain.

I am reporting on our car to give real world driving statistics based on my, mainly my wifes and ocassonaly my driving.

I will add that my wifes really loves the Prius, as her old car was only 20-22 MPG at best and now her mileage has, for the most part, more than doubled.

I also like as well as enjoy driving the Prius, but deep in my hart I still believe I am a diesel man.

alfon

 

You can say that again!

REAL-WORLD data trumps all laboratory studies. They can't account for the crap we actually encounter... like my 10°F commute the other day with a top speed of only 4 MPH. I watched the hybrid system repeatedly cycle. 8 minutes of stealth. 3 to 4 minutes of engine. That was amazing... and something you don't hear about in studies, despite us having to deal with it every single winter.

The variety of trip length, outside temperatures, and driving conditions makes long-term collections of data from actual owners far better than EPA estimates.

Unfortunately, some owners regret not having looked up and understood that real-world data prior to their purchase...
.

 

Yup.

Show me the data!

Here's mine, in raw spreadsheet format... allowing you to draw your own conclusions with... letting the data speak for itself.
.

 

John, I now you are talking about me in the last paragraph of your last post. Needless to say. You would make a big favor to all of us if you too leave me alone. That's not helping it. Some people don't like the way I comment my findings, fine, point already taken, just let it go dude!

 

My mostly highway tank was 48.1 mpg calculated (51.6 MID). The average speed of the tank was 46 mph reflecting 55-65 mph cruising, slow accelerations at the upper end of ECO, and some idling time. MPG was pulled down by idling to keep someone warm while I made a purchase, by letting others test drive the car, by temps ranging from 5-21F, hills, stop signs at the bottom of hills, multiple cold starts, etc. When on the highway averaging 58 mph and including getting up to speed, the MID reported 58 mpg with a modest quartering tail wind, and 51.5 with a modest direct headwind. That is almost 55 mpg average, less 6.8% MID error = 51 mpg calculated highway average (106% of epa 48 highway mpg) at very low temps. Cruise control was used less than 10 of 380 miles because it kills mpg on hill climbs. Instead, I used a lot of DWL.

Cold PSI was 44/42. My grill was blocked 100% lower, 0% upper. The grill blocking was obviously beneficial in reaching normal temps and holding heat longer. But I now suspect it will not help mpg appreciably in any more or less steady freeway driving. For town driving, short drives, under 45 mph driving especially using P&G, stop & go, meal breaks, etc., the blocking will be of benefit. But at speed, the steady demand on the ICE simply seems to produce more heat than necessary to keep the block warm and the cabin warm.

My coolant temps ran 190-195 (never above that observed), but dropped quickly when the ICE was stopped, even with 100% lower blocking. For example, while sitting in drive through line with fan on 2 bars and manual temp at 73F, I lost 40F from the 195 in about 5 minutes (the ICE never lit) while ambient was 14F with estimated 10mph winds. Of course, loss would be slower when not maintaining cabin heat.

High speed, low psi, low temps, and cruise control are all killers. By moderating speed, pressing up the tires, blocking the grill, and using DWL instead of steady speed, I was able to (barely) beat highway epa rating in these low temps. Cold temps are a critical factor in poor mpg in short and slow speed driving, but speed and driving style (e.g., cruise control) are more important on the highway. The winter penalty on the highway drives may have more to do with the denser air than heat loss. So, the loose nut behind the wheel (me) can mitigate the winter penalty by blocking the grill for local driving and by slowing down for highway driving.

 

Has anyone mentioned "resonance"?

I had a long cold-weather drive over the past 2 days, and decided to experiment.

New wheels (open-spoke, no hubcaps) and winter tires (bad rolling resistance), so I was expecting not-so-hot performance - and I got it. The first 366 miles showed 40.9mpg - 39.0 actual. This was running mostly at 72mph, in temps around 27F the first day and 14F the next.

After gassing up, I had about 60 miles left and decided to try running at 69mph (actually did 70mph for a major chunk) - and the reset tripometer displayed mpg of 43.4 (an increase of 2.5mpg). I realize the engine was already warm, but over the previous 366 miles I had only stopped twice, which is more than enough distance to offset that (and I have grill blocking which warms things up pretty fast). And to put that in perspective, the first 215 miles showed 41.4mpg, and the final drop to 40.9 happened over the next 150 miles - so the mileage on the 2nd day was likely even worse than what was displayed because of the previous day's average.

The winter tires are only Q-speed rated, and don't exactly ride "like butta". My hunch is that 72mph (for my tires) hits a resonance where the tires are substantially worse than average - a bump in the resistance curve, as it were. A small change in mph showed a substantial change in mpg.

So my suggestion would be to try driving 2-3mph slower, and/or possibly driving 2-3mph faster and see if the 3 points form a "V" instead of a line/curve.

 

Regarding grille blocking - I think if I had a Scanguage, I would try 100% block lower and 75-80% upper in these temps.

 

I have been considering a little grill blocking as well... our winter weather has zapped my MPGs a bit, but maybe that's because I've had to run the AC this past week or so

 

I'm not surprised the Prius maintains 190 better than a normal car. Part of it's high efficiency comes from running the engine in it's most efficient configuration, which I assume happens at around 190F. One of the reasons they pump the coolant through the exhaust system to heat it up faster. Unfortunately it has the side effect of using more energy when the temperature is cold.

I'm running at 45MPG at the moment, no blocking, but the temperatures in Seattle are quite mild right now. I had a slow leaking flat for a tank and it killed my fuel economy. As far as I can tell, the Prius is much more sensitive to non-optimal conditions than a normal vehicle, but since it's essentially highly tuned for fuel efficiency, it makes sense. Even in the most non-optimal conditions, the fuel economy is impressive, and in optimal conditions, it's simply amazing.

My only gripe with the vehicle is the non-entity of EV mode. It's seriously the most useless part of the car. By leaving the car in normal mode and watching the power gauge, you can achieve higher speeds, for longer, in electric only than you are allowed by EV.
What I would have liked for EV would have been a mode that stops the car from turning on the ICE at all and allows you to drive the way you normally do, just limited to what the electric only can achieve. The motor is rated at 80HP, it's just a pity the battery can only provide 36. The car would have had a lot more "oomph" if the battery could have done justice to the motor.

 

I imagine that someone will soon come up with a hack like they did on the Gen 2. The downside being I suspect that more batteries will be damaged for over use.

 

Here are the results with pictures of my last 2 trips, this time with total grille block in the lower part... Some people asked me to show these photos because there was some questioning about the legitimacy of my findings. No problem.

Pic 1-The actual blocking... It stayed in placed all the time since I put it... even after cruising in the hwy at 75 MPH for a while, the water temp (measured by scangauge) stayed stable at 190-200F.

Pic 2- MID shot from the first trip, my typical 350-360 mile range, pretty flat. Average speed was rather slow (54 MPH) because there was light snow for about 40% of the time and remaining interstate was wet from melting snow. Air temp was 20F and calculated MPG was 41.7 (Pic 4 under Jan 7 in the Gas Cubby application shot from my iPhone). That's another thing about the Prius... the discrepancy between calculated and indicated MPG is insane! As you can see, neither the blocked grill nor the low average speed was able to offset the effects of low air temperature and light MPH snow on MPG. 41.7 MPG is pretty pathetic at 54 MPH...

Pic 3- MID shot from the second trip post grille blocking. Lower air temp (only 14 F) but dry conditions! Speed this time was much higher (68 MPH). Calculated MPG was only 36.9, one of my worst!!! (under Jan 9 on pic 4). I still have to compare these with other trips but it seems that the blocked grille is helping little (if any) in my case. Bummer! I think there is more than a hand full of cars out there (non-hybrids) that can approach or beat 36.9 MPG in the hwy in similar conditions, so that is unquestionably disappointing.

Pic 4- My iPhone app showing my calculated MPG. Note where my lifetime MPG is right now... 46.8 and going down... I believe it will reach lower 40's until it starts bouncing back on mid-spring but it may never reach above EPA estimates until it starts to plunge again on mid-fall...

Pic 5- The final evidence... the chart speaks by itself... my iPhone app tracks my MPG since I started recording it... you can see the plunge on mid-fall... pretty impressive! It actually should be more impressive than this because I got the app after 2 tanks over 60 MPG calculated!!! Does anyone still question my motivation to complaint about the 2010 Prius mileage in the winter?

 

Have you tried the pulse and glide technique? Seems like your long trips would be great to test that method.