Latest Software Update Safety Recall Resulting in 8mpg less...

Here's some data from a 2010 Prius with the update: I did eight 4.3 mile runs (4 x 2 pairs going both directions) on a freeway, averaged 37.5 mph and saw 70.0 mpg indicated. The route was mostly flat, but there were two small, 30 ft high hills. Four of the runs were in Eco mode, four were in Power mode. I set the cruise control to 40 - 41 mph on each run. Temp was 55 deg F. Based on your curves, I should be getting 80 - 83 mpg.

This same vehicle will do 54 mpg avg indicated at 60 mph.

So is this evidence that the update does negatively impact mileage?

 

Thanks!

I will go back and repeat my benchmarks in the 35 to 45 mph range in smaller increments. This may be something found just below the hybrid transition speed, 42 mph.

I may have trouble with the 55F but the density altitude formulas are well known. I will also have to adjust for tire accuracy:

• 0.0702 lbs/ft{3} - 85F, 600 ft, 60% humidity
• 0.0748 lbs/ft{3} - 55F, 600 ft, 60% humidity
• (0.0748 - 0.0702) / 0.0702 = ~6.6% increased aerodynamic drag
• 80 MPG(indicated) * 93.4% = 75 MPG(indicated) expected

According to the weather reports, 54F tonight, and mid 80s tomorrow. But tires are an issue.

I'm on our second set which are Yokohama AVIDs running 52 psi. They run true mph/MPG within 1% between indicated and pump measurements last time I checked last year. I selected them because their revs/mile compensated for the errors of the original tires. This means using the true line, not the indicated. Or we can adjust the current MPG indicated to the previous MPG indicated by 6%.

Checking the calibration is important as tires and air density have direct effects. But I'm about to run out of the low temperatures.

Bob Wilson

 

Ok,

These are not FORMAL results. It was too late last night to get up at 3:00 AM to re-run the cold weather benchmark but I was able to get a couple of practice runs in:

	miles	MPG (ind)	avg mph	CC mph	temp(F)	notes
1	4.2 mi	70.5 MPG	37 mph	40 mph	64 F	7:30 AM; 1/4 mile 25 mph school zone; one complete stop at light;cold-start
2	8.3 mi	99.9 MPG	40 mph	40 mph	81 F	12:06 PM; no stops; multiple overpasses; "N" on descents; GPS: 8.4 mi; 40.5 mph; 45.8 mph peak
3	4.1 mi	99.7 MPG	39 mph	40 mph	81 F	12:25 PM; slow to 25 mph at one light; GPS: 4.2 mi; 39.3 mph;

Although my first practice returned similar numbers to 'Dark_Matter', it suffered several problems: (1) a complete stop, (2) a school zone, and; (3) cold-start, the car was driven ~3 miles, not long enough for a full warm-up.

The second practice shows the problem with the car being: (1) 5 years older; (2) second set of tires (properly inflated and right sized); (3) efficiently driven, and; (4) on a segment with descending altitude:

	longitude	latitude	altitude	start/stop
1	34.769202	-86.586682	207 m	start
2	34.660482	-86.601655	175 m	stop

Google MAP shows it as 8.9 miles. I don't know where Google comes up with the extra 0.4 miles but assuming it is a worst-case rounding error of the least significant digit, 0.2 miles could be the error.

The third practice shows the same characteristics as the second practice on the same route as the first. Since the second and third practice runs were at 81 F and both on descending routes, it may be difficult to repeat the results from 5 years ago. The tires are different, the transaxle oil has been changed three times; and who knows what today's Costco gas is compared to Shell 89 from 5 years ago. I can't use benchmarks that come in at 99.9 MPG because they have 'pegged the needle'. There are other benchmark routes I can try but I have to survey them for traffic and total altitude changes.

I'm also faced with warmer weather. It did get to 54 F between 3-6 AM this morning. But I had to get some sleep. Today is a workday. We are under a southerly flow from a high pressure system so the nights will be getting warmer.

LESSONS LEARNED

• If the cruise control speed != average speed, the run is no good.
• Do not benchmark unless at least 15-20 minutes of normal driving, no cold-start benchmarks.
• Find benchmark routes without lights, school zones, and elevation changes.

LESSONS SUGGESTED

• Changing transaxle oil is a good thing!
• Right-sized, properly inflated, LRR tires are a good thing!
• Efficient driving becomes second nature, stop it for benchmarks!

This is a patched car so the hypothesis of the patch causing a loss in MPG is still and open question. These were practice runs so I need to get more data to compare to the original, from-the-dealer benchmark. I can moderate my use of efficient driving (i.e., not use "N" on descending grades) however I will not back-out or adjust my mechanical configuration from what I normally drive. This is the car 'as is today.' But this suggests an interesting hypothesis.

My properly sized, inflated, LRR tires and multiple transaxle oil changes have over-compensated for any mileage impact of the patch. In effect, I've tuned the car so it out performs what it did off the lot.

Bob Wilson

 

My Prius was completely warmed up before I did my test runs. My tires are at 40 psi front, 38 psi rear. I changed my transmission fluid at 32k miles, and I'm at 73k miles now. My test course is a freeway that's mostly flat with two small up-and-down hills. I just changed my spark plugs and pulled/checked/cleaned my fuel injectors. Cabin fan was on manual. Windows rolled up but sunroof was open a crack.

 

I'll try to get up early enough Tuesday morning to warm the car and repeat the 40 mph test in the cold. Significant differences:

• 55 F vs 82-85 F of original benchmark
• 40 psi vs 52 psi

How far away, months, weeks, are you from warmer weather?

Bob Wilson

 

This Saturday may hit 75 degrees. It took me about an hour to do eight runs. If I'm not working that day, I can try it again.

 

Excellent! I fully understand the need to have time. So this evening, I ran a series of benchmark segments with photos at the end. Two routes were used:

• Baily Cove Rd - flat but with traffic lights, three runs with one having a full-stop due to traffic light
  • 34.671216 -86.53917 203m
  • 34.595117 -86.549447 175m
• Parkway - multiple overpasses but no traffic lights, two runs
  • 34.673419 -86.574613 181m
  • 34.767394 -86.587030 206m
• Stayed on cruise control the whole time with rare, minor adjustments to get GPS reading of 40.0 mph.
• Car throughly warmed up before first benchmark run.

	miles	MPG	avg	temp	dALT	route
1	5.3	91.4	40	60 F	-28m	Baily Cove
2	5.4	65.6	40	60 F	+28m	Baily Cove
3	5.6	85.6	39	60 F	-28m	Baily Cove (stopped)
4	7.0	75.7	40	61 F	+25m	Parkway
5	7.0	86.3	40	61 F	-25m	Parkway

So I'll take the first two and last two runs:

• 5.3+5.4+7.0+7.0 = 24.7 miles total
• (5.3/24.7) * 91.4 = 19.61
• (5.4/24.7) * 65.6 = 14.34
• (7.0/24.7) * 75.7 = 21.45
• (7.0/24.7) * 86.3 = 24.46
• 79.86 MPG = 19.61 + 14.34 + 21.45 + 24.46

I can not replicate your benchmark and at 61F instead of 85F, I got the same mileage as my original benchmark but at a cooler temperature:

1. My car may be mechanically tuned to overcompensate for original benchmark.
   • At 15F cooler, I got the same MPG as at 85F in the original. It should have been lower due to denser air.
   • Second set and a half tires are right sized (~1% error with pump) and at 52 psi, lower resistance than original tires.
   • Three transaxle oil changes have diluted out the original debris.
   • Original benchmarks were with less than 100 miles on odometer and new tires.
   • Current tires have ~1,500 miles on front and ~40,000 on rear pair.
2. My patch may have been done 'better' than others.
   • Perhaps someone knows how to read out the software version and foot-print with miniVCI?
3. Non-linear temperature effect 55F vs 61F
   • Earlier temp vs MPG with NHW11 showed non-linear effects BUT it could have been sampling errors.
4. West-coast vs. North Alabama gasoline
   • There is evidence of regional differences including 'reformulation' common on the West coast.
   • Running E10 but in Alabama, it is a 'no more than' E10.

I can't find evidence of a mileage hit at 40 mph with our car. But it gave the same 80 MPG (true) as the original benchmark 80 MPG (indicated) / 76 MPG (true) in 15F cooler air.


Bob Wilson

 

I took the car in for it's 40K checkup. They still admit that others are also having the problem, there is no known fix, it is up to Toyota Corporation to resolve, and they still can't reapply the safety recall.

In the last 6 months since the last checkup. I have had 5 tanks of gas at 40 MPG or less and 3 tanks above 40 MPG with the best millage being 43.1 MPG (mainly freeway) and the worst being 34.5 MPG (mostly town driving). I have always seen town driving being worse after the recall. Since I was now below the MPG threshold that would make my car "out of spec" being below the 40 MPG... I had high hopes that they would finely do something. It is the worst millage between services and I have done more town driving.

The service manager I was assigned, was not aware of the previous information I had received from Toyota on the 40 MPG bottom end of the spec (but said he would look into it). He told me that there was a problem that all 4 of my tires were underinflated at 30 PSI, where the front tires were supposed to be at 35 and the rears at 33, so all of my MPG data is now suspect even though: (1 They measured it without me, 2) They filled it last service, 3) they looked and there were no problems found with the tires, 4) there were never any automatic warning indicators that the pressure was low (which it would have detected a 5 PSI loss in each two tires when they were last filled and set). He did not believe the tire inflation would explain the majority of the drop.

I have also lost air in the tires (which all 4 being at 30 PSI is suspicious in itself) , nor has my wife's Prius tires lost any air (which still works great at close to 50 MPG). My history of service also supports that. They said they would look into my millage issue, but I have been told that before. They will probably hang everything on the tire pressure (which they last set), so another 6 months of data for them is shot. We agreed that I would come in once a month for them to check the air pressure, but they know others have the issue and didn't have the air pressure issue in their last service.

I reiterated that the problem was mainly on city driving, and tried to get them to have anyone drive around the area with me to see how clear it is by just driving for a little while around their dealership and using the in car MPG calculator. They declined the offer, which would have taken less than 10 minutes. It is obvious, and I can show that sometimes going 12 MPH with the engine warm on a slight decline without the accelerator on, that it will not go into EV mode, and when I press EV mode, it says I m going too fast for EV mode. Sometimes it will, and it doesn't say the EV mode isn't currently available. I still also have the problem where when stopping it does not go into EV mode, and the engine stays on a few seconds after I m at a complete stop with a full battery. But none of this matters to them.

They did seem anxious to buy the car from me and "have it be their problem", although the initial offer was low Kelly Bluebook, so I am not sure if they just wanted used cars, or get mine back.

Toyota and the dealership still know it is a problem, so it is not data that they want or are interested in. They don't want any or clearly see it with their own eyes... so doing any additional experiments or supplying data is worthless, and they will basically tell you that. I wish it was different.

Anyone have any updates from their encounters with Toyota or their dealer?

 

Really sucks when your best recourse is trade in.

 

In November/December, the 4th Gen will be out.

Bob Wilson

 

I have a correction to my last post, I only went back 3 months on my millage records. The correct number should be 8 tanks of gas at 40 MPG or less and 6 tanks above 40 MPG with the best millage being 43.1 MPG (mainly freeway) and the worst being 34.5 MPG (mostly city driving).

I do have to wonder if they are trying to get the problem cars out of the market place, since I don't really see how they can sell them and get 40 MPG or less out of them. The new owners would not be happy and they would have bought them from Toyota with te same49 MPG dance I got. It did get those numbers before the safety recall, but they claim there is no fix.

 

Our (more-or-less) lifetime mpg is 47, translating from 5.0 liters/100 km. We're careful drivers, but not rabid hypermilers. And our car alternates between low profile 17" rubber (on the heavy OEM rims), and X-Ice.

Your status quo of about 39 mpg does not seem right, especially with 15" rims, which are better for mpg. Especially since, if you're concerned about mpg, you're likely trying your durndest.

 

Why are you not checking your own air pressure? I'd not trust the dealership to do it right or to keep it where it needs to be. If your TP was low, you should have already known about it.

 

This is consistent with a problem that keeps the engine running instead of running in hybrid mode when the engine shuts off at every opportunity under 46 mph. This can be caused by a number of non-fault conditions if someone is looking at all of the vehicle data. If you are curious about finding why:

• Windows XP laptop + miniVCI and Techstream software
• 12V to 110 VAC, 50-100 W - optional, just to keep the laptop powered up

SETUP

Install the software and miniVCI on laptop and test with car to make sure it runs. We'll tweak a file so it runs for more than 2 minutes in record mode, 10 minutes being the optimum. It is important that once started, you can do a normal commute. This recording function allows you to share the data with us. Also, make sure you can make screen snapshots so we can discuss what is going on.

Alternative, use the 'Torque' APP with a qualified OBD interface. I understand Torque allows the data to be recorded but we may need a Torque expert to address how. Torque comes with a limited set of metrics and I failed to figure out how to load the 2010 Prius specific metrics. But we only need a few to verify the problem area.

HYPOTHESIS TO TEST

1. Is the engine turning off when it can after warm-up - we need to monitor engine RPM, speed, and coolant temperature. We also need to check shifter position and traction battery temperature and voltage.
2. What is the engine fuel trim, ignition, and EGR valve settings - this is where the Techstream software excels because it has all of these critical metrics.
3. Look at driving profile - there are pathological routes and driving profiles that can really hurt mileage even at speeds under 46 mph. These can be derived from the recorded Techstream/Torque data.

NEGOTIATING POSITION

As long a Toyota holds all of the technical data, you are subject to their interpretation. But with hard data, recorded and compared with working Prius, you have negotiating power that extends outside of the Toyota Service Center. You have data that can be shared with NHTSA as a product defect. You can shop for an attorney to argue your point of view with upper, Toyota management. We can use your data to help identify others who claim the same symptom. The key is with knowledge comes power.

Bob Wilson

 

You got to be kidding !!! In 6 months you did not check tire pressure ?? and then complain about low MPG ??? losing from 35 to 30 will not yet trigger the alarm (I think that is 20 or 25 % loss from the LAST SET !!! it is not an absolute PSI)

running on 30 PSI would result quite a big mpg loss maybe not all...

By the way you can NOT tell by looking at the tire if it is down to 30 psi !!!! it start to show around 25-20 for sure .. but again not checking for 6 month is crazy ...

Also it doesn't even have to loose air !!! If it was set in May on a hotter day and then you check it on September you can easily have that much pressure drop without loosing much air at all .... (but that would mean it was OK during the summer time)

Also you can not even trust the shop. Last time they told me they reset tire pressure to Toyota spec (after service guy arguing with me that it is mandatory for them blah blah.. and I let them do it) ... but turn out the mechanic did not do shit with the pressure it was all the same as I set it 42/40 but reversed since the guy did rotate them ... So I went back showed it to the fuckers .. and told them I am not coming back to this Toyota shop again.

 

gabor, you're gonna give yourself a heart attack.

 

I did not check my tire pressure. In my 43 years of driving, I have tested it a lot over the years but never had a problem unless the tire had a nail. I haven't checked tire pressure outside of the dealer (and when I would get a new or fixed tire) for probably 10 years, and each service report has shown proper inflation. My bad, but hasn't been a problem. Same with oil, I just haven't seen any losses between services. Service has been sufficient until now (1st time). Since all of the tires were at exactly 30 PSI , it is probably more likely it was set wrong at the last service, than actually loosing air. They do a 29 point safety check. Do we not believe them and have to redo all them right after each service? If that is true... why even take it in for them to do?

 

My tires lose about 2 psi per month so I top them off every two months. I carry a 12V inflator pump from Harbor Freight, $12 on sale.

I also set the tire pressure sensor for max sidewall, 51 psi. When I've had a leak, the light came on at 40 psi.

We prefer self maintenance in part because we are curious, save money, schedule on our time, and quality of work. But that is not for everyone.

Bob Wilson

 

But checking tire pressures and the oil dipstick? That's like brushing your teeth and flossing, lol.

 

If you check the oil level you may notice that your car looses oil ... brrrrr better not so you can JUST say " I just haven't seen any losses between services"