2010 Prius III fuel efficiency hypermiling results

I purchased a 2010 Prius III in April 2010. I've been trying out a variety of hypermiling techniques on it since then and I have
purchased a Scan gauge II recently to refine those techniques.
On short 15 mile summer runs the MFD says that the Prius has gotten about 81 mpg; however, the MFD FE computations tends to over estimated the mpg by 3 to 5 mpg so the FE is probably closer to 75 mpg. The overall mileage between tank fill ups (usually about 9 gallons or every 500 miles or so) is much less. On these extended distances, the 2010 Prius computed mpg has been as low as 52 mpg and has high as 64 mpg with the average overall mpg to be around 60 mpg.
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After 578 miles, on my last fillup I computed that the 2010 Prius was getting 61.8 mpg (the MFD estimate was 65.5 mpg).
I finally got to checking the tire pressure and the tire pressure was too low. All four tires were at 30psi, Toyota specs the front tires at 35psi and the rear tires at 33psi. The OEM Yokohama tires are rated for a maximum of 40psi. Many on PriusChat were saying they had set the front tires at 40psi and the rear tires at 38 psi. The 5psi over the the official recommend psi level is suppose to increase FE without causing problems in handling and tire wear. I am a bit worried of setting the front tires at their max psi ratting so I set all four tires at 38psi.
I just installed a Scan Gauge II on the 2010 Prius. The most useful gauge is the instantaneous MPG and the RPM. The Instantaneous MPG shows a finer level of detail than the Prius's MPG bar chart. It is useful to monitor the RPM to see how hard the ICE is working. The AVG (average mpg) seems to output the same number as the Prius average MPG display.
With the scan gauge II and the higher tire pressure, I hope to improve my FE score will improve.
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I've raised the tire pressures to 40psi front and 38 psi rear. Even with the scanguage II - it is still difficult to get the car's computer FE display to register higher than 67 mpg over 200 miles. (my actual top mpg during the summer is probably slightly under 64 mpg). I suspect that with better LLR tires, Michelin E/S, the mpg could be improved by 2 or 3 mpg.
Getting FE higher than 67 mpg appears to depends on finding a better route and given the traffic pattern. To optimize hypermiling a commuting route need to have atleast two lanes in one direction(so other car can past you), have very few stop signs and traffic lights (so you could maintain the vehicle's momentum as long as possible), be relatively flat over a long distance(so energy would not have to be expended going uphill in either direction) , have a smooth road surface (to extend the coasting time of the car), and allow the car to go between 35 mph to 45 mph without impeding the general traffic flow( which is the optimum speed for the maximum fuel efficiency of the vehicle)..
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The Scangauge II on my Prius has indicated that I was able to achieve over 55 miles per gallon by using Plus and Glide(P&G) cycle on a smooth road with slightly hilly terrain. This technique involves briefly accelerating (> 2000 rpm ) to achieve 45 mph and then pulling back on the accelerattor so that the HSI is in the middle of the ECO bar ( about 1200 RPM) and allowing the speed of the Prius to decrease to around 33 mph before attempting to repeat the .P&G cycle all over again.
This technique feels strange at first since the results are better than if one attempts to maintain a constant lower speed (35 mph) and allow the car to decrease its speed slightly(26 mpg) over the same route. While the ICE burns more gas during acceleration if the time of the acceleration burst is kept very short it could burn less gas than if the ICE is kept running at a lower but uniform burn rate over the same amount of time. The Prius because it is very heavy maintains its speed due to the kinetic/stored potential energy created during the acceleration. The trick is to avoid reaching a top speed that is faster than necessary. The top speed should not be any faster that the speed it would take so that if the Prius had to come to a full stop that by letting go of the accelerator one would have enough distance in front of the Prius so it could to coast to a stop. This is not practical in urban driving so a compromise top speed needs to be selected for a given section of a well know route. Knowing a good top speed for a section of road is key to obtaining the best FE results from a P&G cycle. Once the top desired speed has been achived- the driver drops the speed of Prius ICE to its most efficient mode which is indicated by being at the center or slightly right of the center of the ECO bar in the HSI indicator display OR the driver run the Prius only on the electric motors by pressing the accelerator so that HSI indicator bar is on the left side of the ECO.
2010 Prius III, Yokohama Avid S33 (40psi front, 38psi rear), Scangauge II current MPG (fcd) = 65 mpg Overall computer MPG = 60 mpg, 5400 miles
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Colder temperature and the switch over to the winter fuel blend of gasoline has cause the fuel mileage on the last tank of gas ( +9 gallons, 540 miles, 58 mpg ) tp drop about 2 mpg. The sudden drop in temperature and bad weather has made it more problematic to maintain the tire pressure at 42 psi front and 40 psi rear. A drop in just one or two psi will lower the coasting ability of the Prius and cause the MPG to drop - so I've increased the tire pressure to 44 psi front and 42 psi rear. The drop from 70F-50F to 40F-30F temperature range forces the ICE to burn gas to warm up the engine/catelytic converter (or recharge the battery) more often -- after a full warmup cycle the overall mileage(AVG) on the Scangauge II drops by about 3 to 5 mpg.
I tested a sub-route with no stop signs or lights but with many steep short hills verses my usually sub-route with a few stop lights and only a few less steep long hills. ( Georgia/Norbeck vs Georgia/Muncaster/Redland) When subtracting traffic factor (by driving when nobody is using the road) it is easier to hypermile/coast on roads that have fewer longer flatter grade hills than if the roads have many shorter steeper grade hills - if there are only a few stop lights that are easily seen from a distance the driver can alter the car's speed to "time" the car so it does not have to stop at the light (thus conserving the car's momentum) so thus there does not have to be a penalty for having traffic lights. However the penalty for multiple steep hills is fixed. The penalty for using a route with many more steeper hills was about a lost of 5 mpg. Essentially the shorter and steeper the road grade is the more difficult it is to get the downhill MPG gain to overcome the uphill MPG loss. When driving through multiple short steep hills without stopping one must maximize the MPG at each downhill grade to mitigate MPG losses from going up each uphill grade. A short burst of power at the very top of the hill is more useful in gaining speed and momentum ( to go help going up the next hill) than applying the power at the bottom of the hill. To get the best MPG, the uphill speed must be allowed to drop as the car goes up the peak of the hill - attempting to accelerate or maintaining the cars speed uphill will case the MPG to drop. How far one can allows the MPG is heavily dependent on traffic conditions. Because the Prius is very heavy and its power to weight ratio is not all that high - FE suffers more during low speed acceleration and uphill climbing than if it were lighter car or a car with a more powerful ICE/MG. combination.
As the winter approaches - I am investigating blocking the front air intakes to help the ICE stay warm. This requires monitoring the coolant temperature (FWT) so that the engine does not over heat.
2010 Prius III, Yokohama Avid S33 (44psi front, 42psi rear), Scangauge II ( RPM, MPG, FWT, AVG) current MPG (fcd) = 60 mpg Overall estimated MPG = 60 mpg, 5700 miles
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Blocking off the lower openings on my 2001 Prius allowed it to warm up in about half the time, increasing my avg mpg by about 4 mpg doing mostly 11 mile trips.
Tire pressure can also make a big difference. Going from 35 to 45 gained about 5 mpg. Cold temps will lower the pressure. Keep checking as it gets colder. I am currently running 50 psi all around. Good for maybe 2 mpg better than 45 psi.
Went from running 5w-30 Mobil 1 oil to 0w-30. Will be trying 0w-20 at next change in about a month. Should help mpg with the cold weather. Car starts fine in the cold (sub zero F)even with 5w-30.

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In the last four weeks the average temperature has dropped about 20 degrees Fahrenheit and the fuel efficiency of my 2010 Toyota Prius III has dropped from 62 mpg to 58 mpg. When the temperature drops from 60 F to 40 F the mpg drops about 10 mpg using the same route w/ hypermiling techniques in approximately the same driving conditions - the reason it seems is that in stop and go slow urban driving conditions the 1010 Prius ICE must run more often to warmup the coolant/emission devices. To try to boost FE - I am implementing the last hypermiling trick I know - grill blocking. I am blocking the the lower grill by 100% and I will monitor the coolant temperature via the Scangauge II. The objective is to make sure the ICE stays warmer and thus has to run less frequently to keep the coolant and emission device warm.
While some tires have a max psi rating of 50 psi, the Yokohama Avid S33 has a maximum tire pressure of only 44 psi so I've avoided increasing the tire pressure any further than 44 psi (at least for now)..
2010 Prius III, Blue Ribbon/Dark Grey Yokohama Avid S33 (44psi front, 42psi rear) <== hypermiler mod #1, Scangauge II ( RPM, MPG, FWT, AVG) <== hypermiler mod#2 OEM floormats lower grill blocked 100% <== hypermiler mod#3 upper grill unblocked
DC/MD/VA metro area worst MPG (550 miles) = 54. mpg best MPG (300 miles,) =66 mpg current MPG (fcd) = 58 mpg Overall estimated MPG = 59 mpg, 6300 miles
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The temperature in the Washington DC Area has dropped down to a high of 40 F degrees to a low of 28 F degrees. Fuel efficiency on my 2010 Toyota Prius III droped down to an average of 55 mpg for a oneway 12 mile commute - this is down from an average of 65 mpg for the same 12 mile commute during the summer time. The problem is not with the tire's rolling resistance (tire pressures is 44 psi in front and 42 psi in the rear) but with the lower power performance from both the ICE and MG during the colder temperatures. Also using the defroster/heater during the winter lowers the ICE energy efficiency. Furthermore, It takes more energy for the ICE to keep the emissions control equipment at the proper temperature when the outside temperature is near freezing. To help keep the ICE warm - I've started to block both the top and bottom grills - during the 12 mile commute. I am monitoring the coolant temperatures via ScangaugeII via the FWT gauge. The ICE water/coolant temperature is peakomg somewhere between 160 F to 188 F degrees ( If the ScangaugeII FWT climbs to 200 F degrees I plan start removing the top grill blocking ) so far there has been no hint that the ICE might overheat due to the grill blocking. I've notice that grill blocking has reduce the number of time the ICE needs to run inorder to keep the ICE/emission temperature up...
2010 Prius III, Blue Ribbon/Dark Grey,OEM floormats Yokohama Avid S33 (44psi front, 42psi rear) <== hypermiler mod #1, Scangauge II ( RPM, MPG, FWT, AVG) <== hypermiler mod#2 lower grill blocked 100%, upper grill blocked 100% <== hypermiler mod#3
DC/MD/VA metro area worst MPG (550 miles) = 54. mpg best MPG (300 miles,) f mpg current MPG (fmd) = 57 mpg (dropping) Overall estimated MPG = 59 mpg (dropping), +6500 miles
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Temps here in New Hampshire have been in the teens lately and are dropping. With lower grill blocked I am still getting about 6 mpg less than in the summer. Will be getting a scangage II soon so that I can tape over the upper grill as well.
On the pulse and glide technique, I'd just like to add a bit to what you wrote back in Sept. The idea is to put the engine under more load part of the time to reduce the losses due to drawing a vacume against the throttle plates, and then to shut the engine off. This is an old trick used in economy runs with normal non-hybrid cars. The car, with a manual transmission, would be accelerated at full throttle in high gear to a fairly low speed to avoid wind drag. It engine would then be shut off and the trans slipped into neutral to coast.
For the Prius you want to keep the speed down low enough so that when you let off the gas the engine shuts off and stops turning. For my 2001 that speed is 41 mph. Above that speed the engine keeps turning to keep from over speeding the motor/generator. When you let off the gas and the engine shuts down the electric motor starts regenerative braking. There are losses when charging and discharging a battery, so to avoid those losses you gently press on the gas. You don't want to step on it so hard as to use the electric motor to propel the car, because that would drain the battery which would then need to be recharged. The trick is to work the gas so that the car is just coasting, as if it were in neutral. That is the glide, without power. You are basicly doing the same thing as the old car above, but are able to control everything with just your foot on the gas.
The roads around here are mostly 2 lane, and coasting down to 20 mph in a 35 zone with traffic behind you isn't really an option. Under such circumstances I have found that a modified pulse and glide still gives better mileage than a steady light throttle. Let off the gas to shut the engine down, then step on it lightly to use the electric motor to maintain your speed. When the battery gets drained enough, or the engine cools, it will start up again. It will have to work harder to recharge the battery while propelling the car, but the fuel saved while it was off more than makes up for that used to charge the battery.
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Bruce Richmond wrote:

This is essentially the technique I use with my 2010. Since my commute to work ends with a roughly 7/8 mile low-load (all either downhill or level, low speed) run, and my commute home ends with a 2.5 mile or so low load run, I'm able to drive those last sections with the ICE running but the electric motor doing all the driving. This raises my average about 1.1 MPG going to work, and 2.5 coming home. Since the ICE is going to have to run a lot to warm up the next time the car is started, it may as well be charging the battery pack as well. The battery pack is never below two bars when I shut the car off, and is usually at 4 or 4.
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Hypermiling in cold weather ----------------------------------------
The local ambient driving temperature has dropped to a range somewhere beteen 37 Fahrenheit to 27 Fahrenheit with the average about 32 Fahrenheit. I've increased the tire pressure to about 48 psi front and 45 psi rear on the Yokohama Avid S33. The ride is very taut but the Prius tends to coastdown hill much easier at this tire pressure setting. Blocking the top and bottom grills on the Prius has lessen the need for the ICE to turn on to heat the emission catalytic converter and has help keep the fuel efficiency up. Even with 100% blocking on the top and bottom, it takes about 45 minutes for the coolant temperature ( as read by the ScangaugeII FWT gauge) to get to the normal operating temperature of 157-188 Fahrenheit. ( For the first five minutes of driving in this kind of cold weather, the Prius fuel efficiency is between 20 mpg to 30 mpg, After 30 minutes of driving in this kind of cold weather, the Prius fuel efficiency increases to about 35 mpg to 45 mpg. After 45 minutes of driving in this kind of cold weather, the Prius fuel efficency increases to about 45 mpg to 55 mpg. After 60 minutes of driving in this kind of cold weather, the Prius fuel efficiency seems to level off somewhere from about 48 mpg to 60 mpg) - Short trips in cold weather can really hurt a Prius' Fuel Efficiency. Over the last two months that I have been grill blocking, the coolant temperature has only briefly touched 192 Fahrenheit, the ICE has been operating well within its coolant operating temperatures ( Note that I have not driven the car for over 90 minutes during the last two months) For the last four weeks, the Prius mileage has dropped to 52 miles per gallon - a new low. The off brand anti-fogger that I applied on the interior of the windshield has lessen the times I've needed to use the defroster (which has help keep the Prius fuel efficiency higher) but at this temperature I still have to use it occasionally - I am wondering whether I applied enough or whether I should have stuck with a brand name anti-fog application. Because using the heater would lessen the Prius's fuel efficiency, I am not using cabin heat - which makes driving in this weather - a very cold situation. I am thinking that maybe I should get a better driving overcoat (9_9) . It looks like that as long as the *winter formula* gasoline is being sold -- the Prius MPG is going to be significantly less.
2010 Toyota Prius III, Blue Ribbon/Dark Grey, OEM floormats Yokohama Avid S22 (front 48 psi, rear 45 psi) ScangaugeII ( RPM, MPG/AVG, FWT, GPH) lower grill 100% blocked, upper grill 100% blocked
DC/MD/VA metro area odeometer = +7000 miles best FE= 66 MPG (approx 300 miles) worst FE = 52 MPG ( approx 400 miles)
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On 12/29/2010 4:40 AM, Neo wrote:

Good luck on snow and ice with those tires and pressures.
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When he runs into me on the road, I'm going to take his tire pressures and add them to the police report. When the insurance companies start bickering, I'm going to make sure his insurance company knows that he was misusing the car in a dangerous way.
Not covered by insurance, trust me.
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wrote:

Raising the tire pressure has not made the car more dangerous, trust me.
My test indicate that these the tires appear to be designed to handle the additional pressure and that handling and braking are the same. I know because I had the tires set at recommended 35/33 psi setting initially - and I can tell you that the braking and the handling are about the same for normal urban-highway driving conditions. I've read that the Yokohama Avid S33 can be set to 50 psi in the front and 48 psi in the rear - However, I have not tested this setting yet. There is about 8 mpg to 10 mpg FE performance improvements going from a 35 psi front and 33 psi rear to a 44 psi front and 42 psi rear tire pressure setting when hypermiling. However, there does not appear appear to be any additional significant improvement by going over that setting to 48 psi front and 46 psi rear.
So far, I haven't seen any reports indicating insurance companies have any opinion on hypermiling - positive or negative. However, I don't think the police would easily allow you to add something to a police report because that would imperil their objectivity as a neutral third party in the eyes of the court. I am not aware of any judicial ruling about under what conditions overinflation of tires can constitutes a misuse or dangerous use of a vehicle. However, if you have any court papers to indicate this to the contrary I am very interested. So far - I've seen very little substantial and rational evidence on the topic of tire overinflation. I've been experimenting with hypermiling in part because - there is no way to find out what I need to know without experimentation. - if you could provide such information - it would save me alot of time.
Most of hypermiling occurs as speeds lower than 40 mph, with slow accelerations, slowly coming to a stop, yielding to faster vehicles and yielding to pedestrian along the way - its highly unlikely that during this hypermiling experiment I will hit anyone. Hypermiling is a very passive form of driving and tends to extend the time it takes to get anywhere. There are alot of crazy drivers out there but I am driving so slowly that they can easily drive rings around me or I can get out of their way in time.
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In article

Absolutely it changes the handling, away from what the entire suspension was designed to be.
The tires ARE an integral part of the suspension, and in fact those little tire patches are the only thing touching the road.
Change that, and you change the dynamics of the entire car.
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In article

It doesn't matter if the TIRES are designed to handle the pressure. Why would you even incorporate that into your thinking about the dynamics of the car?
Do you believe that all that matters is "can the tires take this"?
And you have zero idea if "braking and handling are the same". All you know is YOU haven't found the edge of the envelope YET.
But you aren't testing it for hundreds of thousands of miles under all types of conditions--that is, until you meet one of those conditions that the car SHOULD be able to handle with an average driver.
When it doesn't handle it the way it was designed to, YOU are the sole factor at fault. Not Toyota.
When you hit me, I will take your tire pressures and add them to the police report.
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Yokohama Avid S33 Tires at these higher air pressures do not appear to have any additional tendency to hydroplane. However, the higher air pressure means that the tires transmits more shock from road irregularities than if the tires were set at alower air pressure. I've only recently upped the tire pressure but I have not notice any problems with traction or handling; however, since I am driving this Prius for fuel fuel efficiency - I am not testing the upper limits tire's handling characteristics or its braking performance as might another. Sofar the tire treads doesnot appear to be wearing out prematurely or wearing out in an irregular manner -- however I will keep an eye on this possible complication.
Reviews suggest that this particular tire has a lifespan of about 20,000 miles - so I am expecting to replace them in the next two years with something better. I've read some negative consumer reviews that complain that the Yokohama Avid S33 Tire have poor snow and ice handling. Earlier this year the Washington DC area was hit by a big snow storm - but unlike certain northern areas of the USA snow storms are a rarity for this area - so I am unlikely to have a chance to test this tire's actual snow and ice handling characteristics before the tire tread wears out
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On 12/31/2010 1:52 PM, Neo wrote:

You won't be hydroplaning on snow and ice, skippy.
You will be skating.
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Yes.
The Yokohama Avid S33 Tires are designed for only light snow - they have only fair snow and ice traction performance. Because, snow and ice are a rarity in my area - it may not be an issue for me since reviews of this tire suggest that they are not likely to last more than another 18 months. When I get replacement tires I am thinking of getting Hankook Optimo H727, Consumer Reports ( July 2010, page 50-51) reports they have very good snow and ice handling characteristics.
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On 12/31/2010 3:09 PM, Neo wrote:

And worse to none at those tire pressures.
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