Colder weather has zapped my mileage to 44mpg

I'm actually running without all covers for the last 4 trips... I like it better without them and the dealer assured me the mileage drop without the covers can be measured in feet per gallon instead of MPG. Anyway, my huge MPG drop came long before I had the wheel covers removed but I have added that caveat to my data in case we later find out it was important.

Dealer did check the wheel that lost the cover for damage and they said it was perfectly fine... they were also puzzled by how it voluntarily detached but it did...

 

I had a problem with losing wheelcovers on my last car. I brought it in for service thinking I had an alignment problem or worse. Their only suggestion was to replace the steel wheels with alloy. I did that and had no further problems. It was "almost" cheaper doing that than constantly replacing lost wheel covers.

 

I wonder a huge drop. What happened in October?
Then, it looks the data is consistent between October and January.
How was the ambient temperature or tire pressure change?
Only the poster knows the why.

Ken@Japan

 

He is saying nothing changed and blamed the drop due to cold weather.

We are trying to piece together more information and found the following so far:

1) Removed the rim trim rings
2) My have hit something that may caused misalignment

 

You sure your wife didn't hit anything? Was there any damage on the run-away cover?

When did you do the first oil change? Is it around October?

You check the obvious things like the parking brake is not engaged, right?

 

My hwy trips started back on Sep, so from Sep to mid-Oct, there was a minor drop going from 50/50 city/hwy to 5/95, but the huge drop in mid-October coincided with the air temp drop. Note that November temperatures were milder than normal here in the Midwest and that resulted in a slight rebound on MPG but it went down again since Dec.

In July my brother went to Chicago from Indianapolis with a friend (roundtrip) using just half a tank with impressive 61 MPG (MID) and 66 MPH, but unfortunately no MID picture was taken. I did several small hwy trips back in July-Aug with speeds similar the ones I drive today and my MID MPG was always above 55...

 

Out of curiosity, though I should probably stay out of this train wreck, do you garage the car, or is it stored outside? Do you need to idle the car for long periods before taking off on these long trips to clear the windshield? You may say, "what the hell does that matter", and I would offer this.

My car sat unused all weekend, and I did not stick it in the garage until late last night. I needed to let it idle for 5-10 minutes to clear the ice of the windshield, front and rear, prior to sticking it in there. Before i put it in the garage, I reset the MFD. My wife drove our kids to preschool today, and when I fired it up for work I was shocked to see it sitting at 33 MPG over 13 miles. I couldn't figure out how she had managed to get it that low, and then I remembered the forced idle. So, ANY amount of idling will bring down your entire trip average. Does this happen in your case? It may help explain another piece of the missing MPG puzzle.

 

That's what she is saying but it takes a lot of noise or shaking for my wife notice anything when driving...

But, my dealer just checked (3 days ago during the 15K service) for any damage underneath or in the wheels... nothing found; however, no alignment was done.

First OCI (5K) was indeed in Oct but after my MPG was already in the low 40's (supposedly they used 0W20 and did not overfill... (I'm particularly stressed about this and about leaving the tire pressure alone at 46/44 psi)... second OCI (10K) was in November in a different dealership because I did not like the first one (no playground or treats for my girls ). 3 days ago, I took it for the 15K service but no oil change since Toyota officially changed it to 10K intervals now. In this last one, according to the dealer, everything was great with the car despite of the 15K miles, tire life was good, there was no need to replace air filter, and they respected my opinion of following the 10K recommendation for oil change since my car is not submitted to "heavy use".

The parking brake is something I always make sure it is completely all the way up and not engaged...

 

Good points. I always start my long hwy trips from a cold start with the car outside and windshield and other windows clean... I actually take the time to clean the windows outside before I turn the engine on... with the right tools it is a lot easier and more efficient to clean out the snow/ice outside instead of waiting the car warm-up inside…

 

Consider taking one of the highway trips when roads are clear and using say Trip B to test (on pretty flat sections of 5 to 25 miles or whatever), the cruising mpg after warmup at 55, 60, 65, 70, 75 mph using cruise, then again using steady throttle in a 10 mph band around one or more of those speeds, preferably including one around 65 mph or less. Your mpg should be a function of cruising mpg, warmup penalty, x number of stops, y amount of climbing, given dry roads and consistent wind. I've seen a thread here on the climbing aspect, but I don't recall that being a major factor on your usual drive. Also, stops and warmup should be minor on this drive, correct? So basically, over the distance, your mpg should approach but not reach your cruising mpg which you can observe over short distances in similar terrain with the MID and/or SG. Your steady state mpg should roughly match say bobwilson4web's data, and if so, then your car would be generally performing to spec.

Also, consider removing the grill block for these drives, to eliminate any aerodynamic penalty, since you and I both suspect any heat management benefit to be small on these trips.

Any moisture, frozen or not, has killed my mpg in every car I've had, so to me, all bets are off in slush & snow.

All of my techniques are the same ones I apply to non-hybrids, so this is 'normal driving' for me. Differences I see between my recent highway tank and your situation: average speed, cruise vs DWL, more climbing for you?, more slush/snow at times for you. Can you see other differences?

Just some thoughts. Good luck.

 

I have considered some of that, but even though my way is mostly flat (no significant climbing), driving short distances at different speeds may be influenced by minimal terrain inclinations... unless I test different cruising speeds in the very same road stretch under the same weather conditions, which can be very difficult to do... but I am considering all possibilities to investigate this, thanks for the suggestions.

My Prius is definitively not normal driving for me. With all my other cars in the past I never really paid too much attention to MPG, all I care was how much money I was spending every month with gas. In fact, unlike my experience with my Prius, I was so used to actually save money during winter because gas prices usually went down in that time of the year, so obviously, my past cars didn't have a considerable MPG drop during winters otherwise I would not have missed it...

 

You may be fighting the system, causing lower MPG. That's a very common trait for owners who hadn't any interest in efficiency prior to buying a Prius.

What happens when you shut off the display?

After all, normal would be to not have any instant MPG info available.
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Those past cars didn't have the ethanol-blended fuel either.
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You got it the other way around.... Your past cars weren't saving money in the Summer or Spring.

 

If I understand correctly, you did not put much attention to MPG in your older car... It may then be difficult comparing your Prius FE (high speed, relation to temp, ...) with other cars you have owned.

Have you thought about comparing your global gas costs for the 08-09 winter (old gas station bills, credit card records, ...) with your current costs with the Prius for the 09-10 winter? You would simply need to adjust to gas prices that obviously changed, but that data is easy to find.

Then you could make fair comparisons between the Prius and your other cars.

Quick note: I agree that the Prius FE takes a huge percentage hit in cold temps but if you rather look at it in MPG differences, you get a different view. In my case, I'm seeing (on a very short commute) a difference of 2L/100km (was at ~4L/100km at >10°C, now at ~5.8L/100km at <-10°C). My old Toyota Echo (Yaris) did 7L/100km in the summer but changed to around 9L/100km in the winter... about the same 2L/100km difference I see with the Prius (and this was tank based, mixing my daily commute with long highway trips on the week-ends, making things look better... was probably worse than 9L/100km on short trips).

I'm still averaging the same 4.3L/100km on the highway @ 100km/h (almost regardless of the outside temp, grille blocked), but at that speed I'm probably staying in the efficiency zone of the car, something you obviously are not with the speed difference.

...anyone knows at which constant speed, on flat ground, the Gen III Prius switches from Normal mode to heretical mode? Always driving above that speed will obviously make a huge difference in fuel consumption... Also, while driving on cruise control at constant speed, the wind, road, driving or not with the flow, flatness of the road, would all make small differences that could add on. Could that explain part of Indyking pathetic abnormal FE?

 

I actually have always paid attention to FE but my way to track it was checking how much I was spending with gas in my commute in a monthly basis. I have had about 10 cars… 7 of which were Hondas, so you think I never paid attention to FE? Believe or not but my gas expenses with my Prius is way more than with any other car I owned in the past and my current Odyssey, but that's just because I have never driven that much before. That's the reason I bought the Prius anyway. But my whole point is... the disproportional MPG drop in the Prius during the winter will likely result in a lifetime MPG much lower than my expectations (I did do a lot of math before buying my Prius). The fact that I have to do all these tricks to maximize its FE combined with the MPG lower than my expectations have made the Prius a very poor value for me, without mentioning my frustration with the rattles/creaks. I would be way better if I just waited 6 more months and bought another car but I took the risk, now all I can do is enjoy the ride and take nice advice from people here who are really trying to help me maximize my FE in the winter... and collecting my data and playing with it is also another way I found to bear my Prius.

 

I wish you waited one whole year of ownership and post conclusive feedback like that.

I wish you waited 6 months and bought whatever car or even the Insight. Sometimes I wish you were sorry you bought the alternative as well.

I wish you come to realize that there are environmental factors that does not allow technology to conserve fuel. The other side of the coin, if it is possible to save fuel, HSD will tap into it. That's the difference with in different seasons.

You can not conclude one way or the other with a tunnel vision but you need to look at the big picture.

Have you thought of why your Honda cars did not get 52% better MPG in the summer compared to winter? Where did the extra heat (that warm the cabin in the winter) go during the summer? Yea.. they were simply wasted through the radiator.

When you have owned 10 non-hybrids, I don't blame you for thinking that way. In fact, things should be the other way around, according to the law of conservation of energy.

It is a good thing for Prius to have "tricks" to improve MPG in the winter. For a non-hybrid in summer and spring, the trick to increase MPG is to make it a hybrid.

 

Grille blocking takes less than 30 minutes. Routine seasonal prep jobs like applying a protective polish and checking the pressure in the spare takes longer. And now that oil changes are only every 10K, that's goes on the before-winter to-do list too. But none of those have anything to do with actual driving.

What are all these tricks you've been talking about?
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Well, if it was based on how much you spent rather than actual MPG, we most definitely should question the FE claims.



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I'm posting once again the quote by egale because it very nicely fits to what I think:

This is pretty much what I am as far as enjoying a car for driving.

I understand some Prius owners enjoy the trouble (to me it really is a trouble) of going through all the possibilities to minimize the winter drop, but that's just not the way I think it should be, and I bet more people than you can possibly imagine think so too. That's no problem though, it's called democracy... freedom to choose. I just made a poor choice at this time.

That's the thing. I am looking at the big picture. Like I said before, I very much doubt that the improved mileage in the warm 5-6 months of the year in this part of the country will offset the huge MPG drop in the winter, at least, not up to my expectations, but we will have to wait until the end of summer for the final word on that. Were my expectations unrealistic? I don't think so, I extensively discussed what I expected with Prius chatters last year before buying my Prius and most people agreed they were very fair expectations. You may or not have followed some of the discussions.

Let me tell you this. This is what the big picture has looked like to me after 10 cars except the Prius: Like I said before, I was never really on top of recording every trip or tank mileage in my past cars but I did check the MPG randomly every once in a while just to make sure the car was delivering what it was supposed to. Every single time for every single car in the past 6-7 years at least, the MPG was always up to my expectations and stable, no matter if it was 100F outside (I did live in TX for a while) or subzero with dumps of snow on the ground. To be quite honest, I first learned that winter can affect MPG just after I started researching the Prius and gen 2 owners were exposing such problem. I moved from TX to IN right before winter and my MPG had actually improved in my previous car (CR-V) at that time because of more hwy in my commute. Winter had no chance to mess with my MPG!

See, trying to convince me the Prius was good idea and me trying to convince proud Prius owners the other way around is an effortless battle with no ending. I just have to do whatever I can to enjoy my Prius and make sure I won't repeat the same mistake again. We all learn from our mistakes...