Fuelly

[theworm]

The sensor can be correct and speedometer still show a little higher then reality. This is becouse its programmed to.
In the BMW I had before ordering my CX-5, the speedo were "corrected" to show a little higher, I unlocked a feature in it to show "uncorrected" speed as digital value on the on-board-computer. Same sensor, diffrent values.
I guess they do it to make SURE it never trick the driver to drive faster then speed-limit. Just a guess.

So I am sure that odometer with original tyres will be correct.

 

[Gio26NJ]

So I signed up for Fuelly recently. On my last tank of gas my gauge showed 28.6 MPG but when I put the odometer figures into Fuelly they show it as 26 MPG. Am I doing something wrong? that figure was taken with an initial Fuel up back on 9/1 and then a second fuel up on 9/10. I always fill to full no partial fuel ups, just confused I guess.

After switching to read tripometer instead of the odometer Fuelly rated my last tank at 29.2 MPG even though the gauge again showed 28.6 MPG close enough! brought my average up .7 to 27.5 now but only 3 Fuel ups. I think Fuelly is more accurate when using trip miles.

 

[Buger]

Note that the tire pressure is also factor in speedometer, odometer and fuel economy readout accuracy. My tire pressure light just came on the other day and I found the tires were all at around 30psi instead of the recommended 35 (17" yokohamas). I like that there is a reminder to check the tire pressure and also like that there aren't any expensive sensors in the tire for it. Mythbusters did some experiments and confirmed there is a correlation with tire pressure and fuel economy. Do not fill your CX-7 tires past the limit though.

http://fandomania.com/tv-review-mythbusters-8-23-minimyth-madness/
Control, 35psi (manufacturer recomendation)
tyres at 10psi = 3.7% increase in consumption
tyres at 30psi = 1.2% increase in consumption
tyres at 40psi = 6.2% decrease in consumption
tyres at 60psi = 7.6% decrease in consumption

 

[markjenn]

It varies from car to car, but it is common to have the speedo be biased to read up to 10% high while the odometer is more/less accurate. This has to do with vehicle certification standards in various countries that allow a speedo to read high, but require that it never read low. To provide some slop for mfg tolerances and tire variations, the mfg is forced to bias the speedo high so that it never reads low.

- Mark