Real-world fuel consumption

[Honda Owner]

I filled the Fit today, 70/30 city/highway, 6.6 l / 100km.

[dr_spock]

8.1 L/100km on my Honda.   Maybe I should ease up on the throttle.

[airbalancer]

OBC read out on the Prius after 1923 km is 4.5l/100km
Cortland Ny to Tom Rivers , missed most of the Poconos Mountions got 4.2/100km driving around 110 km/hr
Tom River NJ to Cobourg 847km, 4.4l/100km, that was driving though the Poconos Mountions with keeping at about 110km/hr
Prius is getting much better hiway mileage then I thought it would get

[Sival]

OBC read out on the Prius after 1923 km is 4.5l/100km
Cortland Ny to Tom Rivers , missed most of the Poconos Mountions got 4.2/100km driving around 110 km/hr
Tom River NJ to Cobourg 847km, 4.4l/100km, that was driving though the Poconos Mountions with keeping at about 110km/hr
Prius is getting much better hiway mileage then I thought it would get

Don't trust the onboard computer much in your Prius. Toyota's fuel economy readouts are well-known to be too optimistic, especially in the hybrids. For example, the british show 5th gear tested a Prius once versus a Jeep Patriot diesel, the Prius' computer said that during their test, the car had done 57 MPG, but when they filled the tank again and calculated by hand, the results were much different, 40 MPG for the Prius. You have to check your trip computer by calculating it by hand over a few fills.

Most fuel economy readouts tend to be a bit too optimistic, better for car companies that their customers believe that their cars get better than they do. Though from what I've seen, Toyota seems to be the worst in that regard. It's rare that you get a trip computer that's too pessimistic, but I've seen it in a Ford Taurus 2005 that always seems to say we get 11 l/100 km, but when I calculated it by hand, I arrived at closer to 9 l/100 km. The Malibu and Aura hybrids also seem to have awfully pessimistic trip computers from what I've read about them*, which is funny for cars that are being sold on their fuel economy.

* http://www.wheels.ca/article/222257 : the readout said 11 l/100 Km, the calculation gave them something like 7 l/100 Km.

[airbalancer]

I did not know that you had scientific measuring calibrated to  NIST for measuring the amount gas you use
My calculation produced 4.5l/100km, but I did not fill the car, the gas jockeys did.

 

[johngenx]

The trip computer in the Corolla is usually within 0.2L/km of what I calculate when filling the car.  That would be well within a margin of error, or "quite accurate."

[airbalancer]

Here is something I read
The difference is:
1. You aren't filling up the tank to the same level each time. Even it you let it quit when the nossle cuts off, its a different fill level. Also different nossles cut off at different times. They aren't all set the same. The -only- way you can know it's filled to the same level is if you fill it -completely-. This is not recommended. It can damage the vapour recovery system.
2. The car calculates the fuel used by the injector firing. This is pretty accurate, but not exact. Your errors indicate a 4-10% accuracy. That's very good!
3. Fuel volume changes with temperature. If the car calculates, say 10,000 injector firings, the actual amount of fuel can be different at different temperatures. The car is unlikely to account for that, as it's not intended to be a lab. quality fuel measurement device. You couldn't afford that!

1 MPG difference at around 50 MPG is 2%. You're fooling yourself expecting that kind of accuracy. Most mileage indicators are +or- about 10%. Add to that the filling inconsistency, and you get the kind of numbers you are seeing.

[tpl]

For the Fit I use the same pump at the same gas station every time and then work out the consumption. For the GTI same but I compare against the trip computer. It matches well enough for government work.

[dr_spock]

I use the same pump at the gas station every time too.   I usually go at late evening when there is no line up at that pump.   

How accurate are the Scan Gauge II calculations? 

[Winklovic]

I use the same pump at the gas station every time too.   I usually go at late evening when there is no line up at that pump.   

How accurate are the Scan Gauge II calculations? 

I use the same pump as well.  After a few tanks of fine tuning, the Scanguage consumption is usually within one or two-tenths of a litre at fill-up.

[Leviathan]

How accurate are the Scan Gauge II calculations? 

After a few tanks of fine tuning, the Scanguage consumption is usually within one or two-tenths of a litre at fill-up.

Yep, there is an adjustment % that you can fiddle with to get it "just right".

[Minou]

Got the ScanGauge II on Monday after ordering it from giffordautomotive.com in Ottawa last Friday PM.  Works really well. $187.40 Cdn including shipping and GST.

Ah, another Scangauge II user. That was a good price you got there, I think it cost me around 200-250 dollars when I ordered it from the manufacturer.

Anyway, with my ION 2.4L manual for the month of August, only commutes (mostly highway) and trips to the cinema or to the store, 2974 KM, 187,6 liters for a total of 6,31 l/100 Km. I beat the Canadian highway rating for my car on 3 out of 5 tanks.

Actually, my total invoice is $183.70, not $187.40.

[Sival]

Here is something I read
The difference is:
1. You aren't filling up the tank to the same level each time. Even it you let it quit when the nossle cuts off, its a different fill level. Also different nossles cut off at different times. They aren't all set the same. The -only- way you can know it's filled to the same level is if you fill it -completely-. This is not recommended. It can damage the vapour recovery system.
2. The car calculates the fuel used by the injector firing. This is pretty accurate, but not exact. Your errors indicate a 4-10% accuracy. That's very good!
3. Fuel volume changes with temperature. If the car calculates, say 10,000 injector firings, the actual amount of fuel can be different at different temperatures. The car is unlikely to account for that, as it's not intended to be a lab. quality fuel measurement device. You couldn't afford that!

1 MPG difference at around 50 MPG is 2%. You're fooling yourself expecting that kind of accuracy. Most mileage indicators are +or- about 10%. Add to that the filling inconsistency, and you get the kind of numbers you are seeing.

I know all of these, but it still remains true that some trip computers aren't very accurate and are actually biased one way or the other. My Scangauge tends to be accurate between 1 and 2% from fill-up to fill-up, but in winter it tends to be around 3 to 5% more optimistic than it is in summer. A ±10% accuracy would be just horrible. I've personally seen it, some trip computers, notably the DIC in recent GMs, are pretty accurate, but some are really off, I mention again the one in the Ford Taurus I drive at work that seems to indicate that the car is a real gas hog, but when I bother to check it on the records we keep for mileage and fuel, it's constantly around 10% too pessimistic. It's not ±10%, it's -10% every single time.

[airbalancer]

 last night on the 401 cruise set to 104
OBC 3.9 l/100km

[Minou]

My first complete (14 days) tankful with the ScanGauge returned:

Scangauge 6.9 L/100 Km vs 6.86 L/100 Km hand calculation or 41.6 vs 41.9 liters actually put in the tank.  I entered the small correction and am surprised at the accuracy of the ScanGauge.

I however entered a +2% correction last week for speed and odometer as those 2 values were too low on the gauge vs shown on the car dials.

 

[tpl]

41.6 vs 41.9 litres. That's one standard Coke can of gas difference in a tank full.

[safristi]

..Jeez...."CAN" the using the same PUMP everytime that's too A*A*............snort of like this................I put it to U that most folks don't really care...and lets face it don't have much choice in the matter...........yer car gets wot it gets due to it's stoichometric tendencies and yer RIGHT FOOT.......................unles yer plugs are burned to a nub and the sensors are fer shizzle......................

[boz]

Just filled up with 37L of regular fuel @ 427.5 km in the trip meter, which runs to 8.7L/100km with my new (well at least to me) 03 Toyota Matrix XR with automatic transmission. 20% Relaxed, rural driving at the speed limit and the rest is all city driving including the times that I've flored it to catch some traffic lights.

After my rusty&dusty 97 protege (RIP) , I am imperessed with the Matrix's fuel economy. 

By the way, being a 6'3" guy, I've found it a real pleasure to get in and out, just like an SUV, but with decent gas mileage. That being said, I don't agree with the others who said the vehicle is underpowered. The power is there when you need it, but then I've used to drive 1.3L diesel cars so being carefull and planning things well ahead is already a habit of mine.

The steering however, is something I'd rate "well below" by anything I've driven before, and no it's not just because it's taller than a regular compact, as I've driven several vehicles those taller than a "matrix", including minivans, luckly it's not in the scope of this topic anyways.

[Honda Owner]

On it's last fill, the Fit got 8.2 l / 100km. This in 100% urban driving, not paying any attention to trying to save fuel and totally inappropriate use of the VTEC feature.

[johngenx]

7.2L/100km on the last 100% all city driving tank in the Corolla.  Still lots of construction delays.