Grill Cover users Post Fillup Mileage Here

[ptjones]

My last fillup was 536.5mi GPS corrected ,11.9gal., 45.1MPG, 50%city and 50Deg.F average temp. Post what kind of improvement you think you have gained.

[zhackwyatt]

May I suggest not to correct for GPS since, not everyone will do that, and then we won't be able to compare apples to apples.

[ptjones]

May I suggest not to correct for GPS since, not everyone will do that, and then we won't be able to compare apples to apples.

I thought about it and in your case it's .5mpg so it's not a big deal, but the CMAX has been getting bad press and anything we can do to put a more positive light is a good thing. Fuelly would go from 37.8 to 38.3mpg not great but good improvement.

[plus 3 golfer]

I thought about it and in your case it's .5mpg so it's not a big deal, but the CMAX has been getting bad press and anything we can do to put a more positive light is a good thing. Fuelly would go from 37.8 to 38.3mpg not great but good improvement.

I finally checked my odometer with GPS yesterday. My current error is 2.1%. GPS miles are 2.1% greater than the odometer reading. I have checked my Garmin GPS many times on long trips vs mile markers vs odometers and always find the GPS to be within a few tenths of a mile of the markers over a 100 miles. When I do take the C-Max on a long trip on interstates with markers, I will check it again. Also, I've never had an odometer show this much error using OEM tires. Of course, this error is good for warranty purposes. :)

 

If my fuelly was corrected, I would show 39.7 mpg instead of the 38.8 mpg at 1388 miles.

 

I would expect a error reduction from the current 2.1% to about 0.6% at the time I would replace the tire (around 3/32). So, if I were to make an adjustment (which I am not going to do) to fuelly, I would adjust the miles for this set of tires by (2.1 + 0.6) / 2 = 1.35% for each fuel up.

Edited January 30, 2013 by Plus 3 Golfer

[ptjones]

I finally checked my odometer with GPS yesterday. My current error is 2.1%. GPS miles are 2.1% greater than the odometer reading. I have checked my Garmin GPS many times on long trips vs mile markers vs odometers and always find the GPS to be within a few tenths of a mile of the markers over a 100 miles. When I do take the C-Max on a long trip on interstates with markers, I will check it again. Also, I've never had an odometer show this much error using OEM tires. Of course, this error is good for warranty purposes. :)

 

If my fuelly was corrected, I would show 39.7 mpg instead of the 38.8 mpg at 1388 miles.

 

I would expect a error reduction from the current 2.1% to about 0.6% at the time I would replace the tire (around 3/32). So, if I were to make an adjustment (which I am not going to do) to fuelly, I would adjust the miles for this set of tires by (2.1 + 0.6) / 2 = 1.35% for each fuel up.

It would appear that my 1.44 is the lowest so far of members commenting so far. I have 9k now but when I first checked it was off by 1.5%. I just think it is off to far not to adjust it. One cover member said he's  off by one MPG.

Thanks for the comment.

Paul

[stephengoldberger]

Be careful in applying "correction factors".  In other vehicles I have observed a consistent bias in the speedometer and odometer, but the trip computer's time-to-distance and distance-to-destination were spot on, using Google Maps to input the trip distance.  No experience with my CMax yet, though (it's still raw materials trundling on the way to the Factory).

[ptjones]

Be careful in applying "correction factors".  In other vehicles I have observed a consistent bias in the speedometer and odometer, but the trip computer's time-to-distance and distance-to-destination were spot on, using Google Maps to input the trip distance.  No experience with my CMax yet, though (it's still raw materials trundling on the way to the Factory).

The only way to accurately compare trip/odometer to actual distance is with a portable GPS. Set both to Zero and go at least 20-30mi or a hundred would be easy to see the difference.  

[valkraider]

You don't need to test via miles. You can test using speed. Go 60mph on the car speedometer, then drive long enough to have the GPS device settle down onto a stable speed. Compare the GPS speed with the Speedometer and you have your percentage of difference.

[ptjones]

You don't need to test via miles. You can test using speed. Go 60mph on the car speedometer, then drive long enough to have the GPS device settle down onto a stable speed. Compare the GPS speed with the Speedometer and you have your percentage of difference.

In my case the speedometer reads 70mph when actual is 69mph yet odometer is 1.5% less than actually traveled.

[valkraider]

69 vs 70 is just about 1% off. That means the extra half percent can be attributed to the analog speedometer. Even leaning your head to one side could change the reading of the speedometer half a mph.

 

Does the engineering test mode screen have a digital value for speedometer? I know it does for tach...

[plus 3 golfer]

One cannot assume that the speedometer and odometer are "synced".  Comparing the analog speedometer to GPS speed is not a good method to determine the accuracy of the odometer due to "reading" error and possible offsets to the analog gauge.  If the digital speed in test mode is "true speed" (no multipliers in the conversion of speed sensor data to digital speed), then it should be good to use.  On my old VW Passat I could display digital speed on my Climatronic by putting it in a test mode.  There was a 2-3 mph difference at 70 mph between the speedometer and digital speed yet my odometer was virtually spot on.

 

I have yet to find a US standard spec for speedometer accuracy or odometer accuracy that applies to cars. Remember Honda was sued about their odometer accuracy and subsequently changed their standard. IIRC, the bandwidth around the accuracy favored them significantly which would affect warranty situations.  It was more likely that their cars over reported actual miles than under reported actual miles.

 

Since Ford sell cars around the world they may follow this standard for speedometer accuracy which has been adopted by many  countries.  This standard allows significant overstating of actual speed on the display.  I know from my days on TDIClub, that especially Canadians were reporting significant errors in their speedometers.  Under this standard, using a 100 km/h test speed, the speedometer could read 100 km/h minimum and as high as 114 km/h.  If the odometer was tied to the speedometer under this standard, the odometer would be over reporting actual miles like the Honda case.

 

From the United Nations UNECE Reg. 39 - UNIFORM PROVISIONS CONCERNING THE APPROVAL OF VEHICLES WITH REGARD TO THE SPEEDOMETER EQUIPMENT INCLUDING ITS INSTALLATION

 

 

The speed indicated shall not be less than the true speed of the vehicle. At the test speeds specified in paragraph 5.2.5. above, there shall be the following relationship between the speed displayed (V1 ) and the true speed (V2).

0 ≤ (V1 - V2) ≤ 0.1 V2 + 4 km/h

 

 

Edited February 21, 2013 by Plus 3 Golfer