calculated vs. computer MPG - Please post your results

Last fill up, 54.0 indicated / calculated 50.13 mpg
Costco Reg gas with 10% Ethanol / winter blend
80% hwy driving 20% city

Temps 33-48 F

 

My last 3 fillups have been 59.1, 59.4 and 58.8 calculated at the pump.

 

Here are my observations for winter and summer time (all values in l/100 km)

December - February -15°C (5°F) to 5°C (41°F)
5.11 - 4.8 = 6.5 %
4.93 - 4.6 = 7.2 %
5.62 - 5.1 = 10.2 %
5.14 - 4.8 = 7 %
5.87 - 5.4 = 8.7 %
--------------------
5.33 - 4.94 = 7.9 %


August - September 15°C (59°F) to 30°C (86°F)
4.43 - 4.2 = 5.5 %
4.47 - 4.2 = 6.4 %
4.48 - 4.3 = 4.2 %
4.45 - 4.2 = 6 %
4.67 - 4.3 = 8.6 %
4.65 - 4.4 = 6.1 %
--------------------
4.53 - 4.27 = 6.1 %

In winter the computer lies even more than in summer or maybe our fuel pumps lie more?

And finally difference between winter and summer
5.33 - 4.53 = 17.7 %

I'm trying really hard not to use heater as much, but it's really hard to get bellow 5 l/100 km in winter conditions. Daily commute to work is only 20 km (12.5 mi) one way so this is partly fault for bigger winter consumption and of course no garage ...

 

Here are my results for 2.25 years. You have the fuel consumption through the year (day 0 is January first), and the error through the year... Who's lying ? The car or the pump ?

I live in Montreal, Canada. Summers average of 20 - 25°C. Winters average of -5 - -15°C.

 

Just re-fueled and got a 44.2 mpg. I can't wait for the colder temps. to go. Even though it's been very mild here for Winter time it's killing my mpg's. Since I got my Prius in Nov. I've only experienced the crap months. I will be smiling in May!!!!!!!!!!!!!!

 

Getting 60.8 MPG by trip computer for last tank, 59.3 MPG calculated at the pump.

I don't know how people are achieving the famed 70.0 MPG.

One thought is that if you do NOT fill your tank up, keep it at 1/2 full, thus less weight in the car, thus more fuel savings. Gas weighs 6.1 pounds per gallon. So 5 gallons x 6.1 = 30.5 pounds of extra weight saved.

 

How do you get 60 at all? I mean, do you live in flat land at 25C weather all year round?

 

Hi thanks for the question!

Current weather is 65F-75F degrees in the daytime and 42F-46F degrees at night. No it is not flat, there are some hills but no huge long climbs.

Here are some tips below (all info below are from priuschat forums by other members hard work

1. Do the pulse and glide method where possible. Sometimes you have to get up to speed quickly then ease up on the pedal and gently depress it again so that we can run on electric more than engine power.

2. Inflating the tires more to 42 front and 40 back really helps a lot. (still below max tire pressure on tires) Do not over inflate tires beyond their designed capacity. See the Prius operating manual for guidelines on tire pressure and filling and the tire wall itself for max pressure and the dealer. Keep all 4 tires the same brand and type. Use a energy saver type of tires.

3. When you are below 41-45 mph (sweet spot varies) release the pedal and slightly depress it again, glance at the instant mpg meter on the dash if it shows 75-100 mpg you are mostly or all on electric power. You will find that if you are doing 41-45mpg and have the pedal depressed like a normal driver would then you are running in gas mode, however if you depress the pedal and slightly press it again to keep speed you will find that you are mostly running in electric mode even at those speeds.

4. Keep your speeds on freeways/roads at the posted speed limits. The faster you go the more fuel you use. ( be safe and smart )

5. If you know there is an exit / red light in front of you and no one is behind you, just glide to the exit / red light. Be safe when doing this make sure you keep up your speed when needed and use the brakes when needed to stop.

6. Don't slam on the brakes, to stop at a red light / exit / traffic etc if you don't need to... if you know these things are going to happen, you can just adjust your driving habits and be safer at the same time. So if you see traffic or a red light etc up ahead, then glide where possible and or slight depress the brake petal so that the brake indicator show that it is regenerating power but not using the friction brakes to stop. Then when you fully need to stop apply more force to the brakes, if you are really good you can stop just but doing regenerating braking power. Use brakes when needed to stop, be safe.

7. One trick if don't fill your gas tank ( I do however fill it full ) if you fill it to 1/4 tank or 1/2 tank the car weighs a lot less and you will get better mpg. You get 1-3 mpg more when tank has less that 1/2 in it. Gas weighs about 6.1 pounds per gallon.

8. Driving with only 1 person if possible, if you have a family and they are in the car with you and a bunch of stuff in the trunk that will decrease the mpg since the car is much heavier thus takes more energy and uses up more fuel. It is a family car after all!

9. Clean/replace the engine air intake filter and cabin filter, a clean filter uses up less fuel.

10. turn off heat, a/c, radio, keep windows closed or use them sparingly.

11. trips of less that 5 miles decrease mpg since it takes time for the hybrid stuff to heat up and get used so you are running fully on gas at this point.

12. Go easy on the car, whats the rush, when you need to get up to speed do it quickly where required, if you don't need to get up to speed quickly take it slower to get up to speed. It is a Prius, we all know it isn't going win any races, so why try. Be smart when driving, be aware of your surroundings and drive safely.

13. Be safe, be smart on the road, keep the blood pressure low, have more patience and see your mpg go up!

14. Use cruise control as well on long stretches mostly straight roads, some people will argue that this decreases mpg, however, keeping a consistent mph is more important than varying my speed constantly by keeping the foot on the pedal. Glance at the instant mpg meter to see if you are running more on electric than gas. Cruise control will not engage if you are under 23 mph.

It is mostly driving habits, we are all in a rush these days, all want to gun the engine and slam on the brakes. Take it eeeaaaasssssyyyy you will find that you will still arrive at near the same time but more relaxed and more aware of the surroundings at the same time. Be safe and keep your eyes on the road and be aware of cars, people around you while driving.

 

Maxmpgcar - thanks for all the inputs - I actually wrote this also posted on PC somewhere

Apart from the 2 above, I essentially do already everything you mention. My question was more related to whether you could get those averages in winter temperatures. I can manage to do around 4 in summer/spring in city traffic, but not in winter with winter tires... I should have been more specific.

Regarding the points above:
- temperatures here have been around -10C/14F the last 2 weeks - the average is therefore around 5.5L/100km-40/42mpg...
- I am too lazy not to fill up to the max and I need to do that also because I have to make sure I fuel as much as possible when the price of gas goes down - currently the price of 1L of regular gas is 1.55€, or 7.7$/gal at current €/$ X-rate...If I see the price down to 1.45, I need to fill it up to the brink!
- with 14F I *am* using the heater - I try to use normal mode at the beginning to heat up the cabin quick, and the set to ECO mode to make sure the engine turns off at traffic lights. By doing this I don't freeze my a** off and my mpg has not being hit too bad.

Now temperatures are around 40F/5C, so I will return down to 5L/100km in city and possibly below that. The average you see in my signature is heavily affected by trips through the alps (on highways) when travelling to Italy - my average there, at EU highway speeds (around 120/130km/h-75/80mph - you cannot practically go any slower), is around 5.4L/100km-42/44mpg.

Clearly where you live, you have the perfect temperatures to best fuel consumption...lucky you! Maybe in summer it's much hotter than here?

 

Hello pakitt

If you drive 75-80 mph your mpg should be around 40-46 mpg in the winter. From what I have read that is about right for your weather, driving conditions and speed. In the summer it should go up some maybe into the 45-50's mpg. Sounds like you are getting the correct mpg from what I have been reading around here. Those are fast speeds and it sucks up a lot of gas! Winter tires also affect mpg, the added friction reduces overall mpg, especially if they are studded winter tires.

Cost of $3.43 a gallon for gas here last week. Summers get very hot around 110F.

 

Another reason to loose those extra 20 pounds around my mid section.

 

I doubt if 30 lbs is going to make any noticable difference in mpg.
During the summer a round trip to San Francisco and back netted a calculated 54 mpg, this is with 3 of us in the car and luggage etc.
Gross vehicle weight on a certified Oregon Dept. of Transportion scale was 3,850 lbs.

 

We Europeans are crazy we pay 7+$/gal and drive 80-90 MPH on the highway. Last skiing trip I manage 40 MPG, and it was not all highway driving, for this type of driving diesels are more economical choice (remember diesel is cheaper than petrol in Europe).

On normal summer commute to work I manage over 50 MPG (no highway)

 

Diesel is higher than regular gas here in the U.S. Here in the
state of Oregon diesel is at least 10% higher than regular gas (petrol in Europe).

The last time I bought gas, last week I paid $3.389 / gallon at Costco regular gas. Diesel at the Fred Meyer Store down the road, Costco does not sell Diesel, was $3.979 per gallon.

alfon

 

I know this is not the right thread, but after the (somewhat frustrating) post of maxmpgcar, I was so happy today to manage what you see in the image attached, that I had to share it here - to remind everybody living in cold areas of the planet, that the Prius can still deliver excellent fuel consumption (add 6.44% average error) even when it is around 0C or less...
And it also means that I am doing "everything right" to get the best FE from my Prius, and sometimes the alignment of planets (like today apparently) does help...

Conditions:
- standard commute route
- return trip with no traffic since done later than usual, but not much more different than other days in earlier times
- a strike of good luck with the traffic lights this morning
- lack of the usual traffic this morning
- -4C/25F
- A/C on Auto set at 19C/66F (as usual)
- ECO mode
- radio ON (volume 30)
- headlights on both this morning and this evening...
- shown is the overall trip
- tires should be still around 2.7/2.8 bar - 40psi

Essentially when it's -10C/14F or less (like it has been the past 2 weeks - one morning arriving to the office I had -18C/0F), and there is traffic and I feel particularly cold (hence set the A/C to 20C and drive in Normal mode for the most part of the trip in the morning - otherwise it never gets warm enough and I freeze my a** off...), I cannot get anything below 5.5L/100km-42mpg.

BTW: Today gas in Munich was at 1.56€/L (or 7.8$/gal) in selected gas stations - I have seen even higher ones at 1.6+€/L this morning...in Italy it is even worse, at 1.8-1.9€/L...

 

Filled yesterday.
393.5 miles traveled
6.513 gals pumped
60.417 MPG calculated (62.3 computer MPG)
Shell 87 octane (10% ethanol)
$4.479/gal.
$29.17 total
$.0741/mile

 

paid $20.35 at $3.52 gal. Drove 306 miles put in 5.784 gallons. Computer said 57.3 mpg actual seems to be 52.9mpg. weather has been around 40 to 58 degrees most of the time. Cold weather doesn't seem to affect my mileage too much, but I don't use the heat much either. I do mostly highway driving and switch to eco mode on the local streets most of the time. like the gas mileage, but find the car much noiser than my 96 camry and less fun to drive.

 

To all posting here - could you please post also the difference expressed in percentage ("%")?
A 2MPG difference at 60MPG is different than at 50MPG.

Simply calculate (MFD - Multi Function Display):
(MFD MPG-calculated MPG)/MPG MFD*100=% error

For example:
62MPG MFD
60MPG calculated
error 3,2%

52MPG MFD
50MPG calculated
error 3,8%

Since it is not clear yet whether the error is constant with increasing MPG or not, posting only the absolute difference (i.e. 2MPG off) does not give an idea of what is going on.
Sorry for the "rant" and thanks for understanding.

 

I filled up yesterday. Drove 468 miles on 9.49 gallons.
MFD 51.3 MPG
Calculated 49.3 MPG Error 4.05%

I live in Hawaii Temp was 65F to 80F.
70% highway, 30% city.
Drive mode normal (no lights on).
Driving Style I don't hypermile, I just drive normal with the flow of traffic.

 

Got my 2011 Prius II one month ago. Did two fills already.

1st tank (shell 87 with 10% EtOH), MFD 49.1 mpg and calculated 47.6

Today I filled 2nd tank (Gulf 87 10%MeOH?). MFD is 51.5 and calculated is 47.5
I am in Boston area and the temp was around 25-50.
I still got MFD around 54 mpg before the snow storm comes 3 days ago.
Need to improve the skill on Hybrid system.