Gen 4 Prius with 15" wheels - Combined (mpg)

[thecaretaker]

This is just something I have noticed recently.

I know the figures car manufacturers put out about MPG are usually on the high side and not normally achievable (except in perfect conditions), but when I purchased my Prius, the stated MPG for the version with 15" wheels was 97mpg. I am sure I remember seeing a giant sticker over the windscreen of a Prius in the showrooms saying 97mpg.

Has something happened for this to change? Only looking on the Toyota website now, it says 'up to 83.1mpg (combined)'. Has the way Toyota calculated the mpg changed or has the Prius changed and is now only achieving 83.1mpg?

I just wondered if anybody knows what has caused the change. Has some EU rules altered the way car fuel use is calculated?

[BhxTrev]

Paul, I've had 2 Prius cars. My previous Gen3 & my present Gen4. Neither of these cars have ever given me anywhere near over 80mpg. I've maybe got something around 70mpg occasionally but generally on a run I get something around 64mpg. I do have the 17inch wheels but that shouldn't  make that much of a difference. After saying that I'm still happy that I'm getting the mpg that I do having had real petrol gobbling cars in the past that were about the same size as a Prius but cost a fortune to run. My only gripe is that I wish manufacturers were a bit more realistic with their figures when quoting mpg! 

[FROSTYBALLS]

Previously manufacturers had to use fuel consumption information gained from the New European Driving Cycle (NEDC) tests in advertising, etc. The NEDC was last updated in 1997 and the disparity between these tests and real world fuel consumption widened over time.

NEDC has been replaced by a new testing regime - Worldwide Harmonised Light Vehicle Test Procedure (WLTP) - which is supposed to more accurately reflect real world emissions and fuel consumption.

See: https://www.autocar.co.uk/car-news/industry/new-wltp-emissions-test-when-its-force-and-how-it-could-affect-your-car

http://wltpfacts.eu/wltp-discrepancy-laboratory-road-performance-cars/

[danowat]

The quoted (old figure) 70.4 for the gen3 is definitely achievable, but i would call into doubt that most 'normal' drivers, i.e. those that aren't quite as anal as i am, would be able to achieve it consistently in perfect conditions, let alone in the winter. 

Glad that they have changed the testing protocol to better reflect the economy in normal usage. 

[FROSTYBALLS]

Also see

https://www.toyota-europe.com/world-of-toyota/feel/environment/worldwide-harmonized-light

The revised test has given the Prius higher emissions figures, although these won't affect the London congestion charge exemption zone, as TfL won't be re-evaluating existing models -

https://www.autocar.co.uk/car-news/new-cars/new-toyota-prius-co2-figures-push-it-over-congestion-charge-exemption-zone

The new test does mean that manufacturers may withdraw or modify models which don't meet the new standards - eg. 

http://www.autoexpress.co.uk/volkswagen/golf/103993/volkswagen-golf-r-power-dropped-down-to-296bhp-due-to-wltp-emissions-rules

[thecaretaker]

Thank you Frosty, I don't know how I missed all these changes. That explains it perfectly. 🙂

[Catlover]

Got my 66 plate Gen4 Prius Excel with 15" wheels just over 3 weeks ago.

Driving home was getting 91.0,mpg over 98 miles (dash photo elsewhere on Prius forum). Car now done 581 miles and 81.1mpg.

[FROSTYBALLS]

26 minutes ago, Catlover said:

Driving home was getting 91.0,mpg over 98 miles (dash photo elsewhere on Prius forum). Car now done 581 miles and 81.1mpg.

Figures recorded by a vehicle's computer tend to be optimistic - have you tried calculating the consumption on a brim-to-brim basis.

[Catlover]

I see the figure on the dashboard, I know its not strictly correct, and so do majority of punters on here, so each can deduct what they want - I still very happy with the figure shown.

[PeteB]

I've recorded every single fillup in all 7 Prius I've owned since 2002 for over 300,000 miles and logged them in a database where is also record the B trip MPG, resetting B at the time of each fill.

The database shows me the actual mpg, difference in mpg and %.  On all versions the % varies between about 2% and 8% but roughly on average about 5% seems right, so that's what I deduct from any displayed figure.

[QuantumFireball]

The US EPA fuel economy ratings are generally a lot more comparable to the real world:

https://www.fueleconomy.gov/!Removed!/Find.do?action=sbs&id=39752

52 US MPG = 62 imperial MPG.

Don't know which size wheels this was tested with, though. Of course there are a lot of car/engine combinations sold here that they don't get, so it's not always useful.

[Catlover]

Today I have owned my 66 plate Gen 4 for exactly 4 weeks, so I thought I would put some fuel in. When I filled up after leaving the dealer, I kept pressure on the trigger until it clicked off, waited a few seconds then squeezed the trigger again until it clicked - tank full.  

Today I did exactly the same procedure. Result was 34.14 litres in 602 miles. Changing this to mpg and it comes to 80.16 mpg. At that point the dashboard was showing 80.4 mpg - not a massive difference and about  .15% discrepancy.. 

Very happy with that.  Of course, after another 600 miles (or whatever) and the reading becomes more accurate.

[kithmo]

Good result Joe, recent warm weather helps as well   

[Ten Ninety]

18 hours ago, Catlover said:

Today I have owned my 66 plate Gen 4 for exactly 4 weeks, so I thought I would put some fuel in. When I filled up after leaving the dealer, I kept pressure on the trigger until it clicked off, waited a few seconds then squeezed the trigger again until it clicked - tank full.  

Today I did exactly the same procedure. Result was 34.14 litres in 602 miles. Changing this to mpg and it comes to 80.16 mpg. At that point the dashboard was showing 80.4 mpg - not a massive difference and about  .15% discrepancy.. 

Very happy with that.  Of course, after another 600 miles (or whatever) and the reading becomes more accurate.

That is good going, although the discrepancy between on-board and 'actual' looks a bit small. Pete's suggestion of 2-8%, averaging 5%, matches my own experience. Were you at the same pump at the same filling station? If not, then the 'actual' calculation could be a lot less accurate than one would expect as the automatic cut-off can be more or less sensitive at different pumps.

Not trying to take away from your achievement at all - even if you knock 5% off your figure it's still an excellent result - but on-board readouts are consistently optimistic in my experience and it might be that next time you fill up, the disparity will be much greater. Please keep us posted anyway - I find this kind of thing inordinately interesting!

[Catlover]

Hi Jay - not the same pumps, first one was where I picked up the car (Solihull), yesterday was Ellesmere Port, near where I live, but 100 mile from Solihull. Of course, as time goes on it will all be more accurate, and sometime soon when the weather changes I will do a test for the winter. 

The Gen3 I traded in was doing 66.2, and I was pleased with that, but the Gen4 is a lot better.

[Ten Ninety]

33 minutes ago, Catlover said:

The Gen3 I traded in was doing 66.2, and I was pleased with that, but the Gen4 is a lot better.

The Gen4 improvements in efficiency do look to be genuinely impressive in the real world, regardless of whatever the WLTP or NEDC might say. Although I'll be sorry to see the NEDC measurements go - I found part of the fun of owning a car like the Prius was the challenge of trying to match those artificial mpg numbers!

[Heidfirst]

38 minutes ago, Ten Ninety said:

Although I'll be sorry to see the NEDC measurements go - I found part of the fun of owning a car like the Prius was the challenge of trying to match those artificial mpg numbers!

Over  the years I have found in my non-hybrids that it was possible to achieve or even exceed the NEDC figures but only under certain circumstances - probably not a surprise as that is exactly how they were set in the first place! 😜

[PeteB]

1 hour ago, Ten Ninety said:

...the automatic cut-off can be more or less sensitive at different pumps...

Also, if one forecourt slopes and another doesn't, it can make a dramatic difference.

I've always brimmed the tank each time, but found (on Gen 1 & 2 Prius) a Gulf station I used to go to near the M25/A1 interchange had a very steeply diagonally inclined forecourt, where the filler at the rear nearside was much higher than the front offside corner.  I could get about 2 more gallons in there than at any other station, and often did over 200 miles before the first of the ten fuel gauge bars disappeared!

I once got 10¾ gallons in the 11 gal tank on a Gen 1 Prius at that station (although the reserve bar was flashing, I'm sure I had at least a gallon still in the tank).

Some say brimming is bad practice, but even on the Prius I had for 9 years & 163,000 miles, it didn't seem to cause any problems).

[Ten Ninety]

2 hours ago, Heidfirst said:

Over  the years I have found in my non-hybrids that it was possible to achieve or even exceed the NEDC figures but only under certain circumstances - probably not a surprise as that is exactly how they were set in the first place! 😜

Agreed - I have yet to find a car that I can't average the NEDC combined measure on an extended journey, but it definitely takes the right technique, the right road, the right weather and a healthy dose of luck!

I came very close to averaging the 70.6mpg NEDC for the 17" Gen3 over a whole year, but that did take a certain amount of dedication to the cause. I think hitting 235mpg in a Plug-In over the year might be a challenge but I should be on electric for nearly 50% of the miles, which I think is similar to the NEDC test so who knows? Once I finally find a car to buy, I'll give it a good go!

 

[YarisHybrid2016]

The Yaris is pretty good on the computer vs. reality, also showing about a 5% optimistic reading (interestingly, this is about what the speedometer is over-reading by too, so I think the actual fuel metering is very accurate).

If I get the computer reading 65+ after a journey, I'm happy. Over 35-odd miles I can get it reading over 74 MPG, but that is very journey/route specific.

Even if the cars don't hit the book figure all the time, show me another car that can do this milage with such little fuel usage??? 😄

Generally, the longer the journey, the happier she is. Just recently I started doing a regular run of 50-odd miles, and I'm hitting the high 60s/low 70s. On very long journeys (300 miles) I get about 70 MPG (real; 75 indicated). Fuel usage is 14.5 L on such a run, so she can do about 600 miles on a tank (7.5 gallons) under favorable conditions.

A major point is to absolutely completely and totally (hyperbole much? 😛 ) avoid the power band, and even one tick mark below that. That and steady cruising at around 53 MPH, and she'll go forever on nothing.

I've also found driving at 40 MPH or so is best for the first minute or three of the warm-up period. More experimentation required, but so far I have actually consistently noticed it does well when I've done this.

[Catlover]

Some good info there, Aaaaa (YH2016)

[kithmo]

8 hours ago, YarisHybrid2016 said:

Even if the cars don't hit the book figure all the time, show me another car that can do this milage with such little fuel usage??? 😄

 

Automatic as well.

There is no 1.5 or 1.8 petrol Automatic that can touch the Toyota hybrids on mpg, even the diesel manuals are very few and far between that can reach these sorts of mpgs in real world figures.

[Catlover]

My Gen4 mpg has now dropped to 79.6mpg, that over almost 1200miles since getting the car close to end of July (2 months).   Finding it harder to get the figure up to 80mpg now, I reckon the drop in temperature has started to have an effect.  There again, my longest run recently has only been 40 mile return, rest of journeys have been shorter.

[altocumulus]

I've usually experienced a general drop in average consumption of 5-10 mpg during the winter months - it'll be interesting to see how the phev copes with our winters.

I also need to find the 'sweet' spot in terms of mph - the last thing I need is tail-gators objecting to me trying to achieve good mpg at their expense 😄

[Catlover]

The last few days we hit 23 degree here near Chester and my mpg has been getting better. I was flabbergasted last night when I read one of the computer screens in the car. Yesterday I had done 64.1 miles, this was over 3 journeys. First one was 3 miles each way with about 2 hours inbetween (so engine cold), then I did journey of 18 mile each way with probably 30 minute inbetween, and the evening I did a journey 11 mile each way with 2 hours inbetween so cold engine again. The mpg for yesterday was dead on 87 mpg. I was amazed.  Really good figure from my Gen4, and such a comfortable relaxing drive. Love it, love it, love it.