Optimistic Fiat? (1 Viewer)

[Geoffers]

After 2 years of ownership I decieded to do a fuel mileage check on my Swift Escape 664,
Fiat 2.2 , 100 bhp. This was a trip to the Norfolk coast with a Fiat Panda in tow, a trip of 325 miles. I filled up again with 59.17 liters (as near as matters 13 gall, thus giving 25 MPG although the trip computer read 30.9 MPG. I also noticed on the trip that the speedometer was 10% optimistic compared with the snooper s 700 sat nav ,which I have always assumed to be the less accurate, how ever numerous speed indicator signs confirmed that the Sat nav nav was correct. I therefore wonder if the mileage reader is also 10% optimistic?
Any comments on fuel consumption & instrument readings.

 

[Terry]

Hi you seem to have sussed it yourself the only way to get accurate MPG figures is brim to brim filling :thumb: It may also be worth noting a accurate mileage check because I have had in the past a van that said I had traveled 124 mls but I knew from other vehicles I had only gone 117 mls for the same journey I put this down to a electronic speedo that was I suspected dodgy
terry

 

[BobProperty]

Almost certainly it is optimistic. Mileometers were allowed a tolerance of IIRC 10% at 30 mph. I don't think that has changed. They always read on the optimistic side i.e. said you were going faster than you really were, because legally that would be the safe thing to do and marketing wise it sounds better. Given that the only source the trip computer has of distance covered will be from the mileometer then it will be optimistic.

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[Bailey58]

Don't forget to factor in all the hills in Norfolk, they're bound to affect the consumption!

I'll get me coat

 

[hilldweller]

Optimistic, bad design or fraud ! You've got to wonder.

The ECU knows it turns on an injector for, say, 10ms. It assumes a certain flow and so a certain amount of fuel used. But in such tiny quantities can they be accurate to 1 or 2% at all temps, pressures and injectors ? So maybe not fraud but programmed to show the best possible consumption.

Speedo, GPS rule OK. For legal reasons they all read low but that does not mean the mileage is inaccurate. You can check this easily on a motorway.

 

[aba]

hi.
i have known mileage to be a bit out due to tyre wear as the tread wears down the circumference of the tyre decreases and therefore needs to rotate more to cover same distance but the counter works on a given distance for each rotation of the wheel.

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[pappajohn]

The Motor Vehicles (Approval) Regulations 2001[12] permits single vehicles to be approved. As with the UNECE regulation and the EC Directives, the speedometer must never show an indicated speed less than the actual speed. However it differs slightly from them in specifying that for all actual speeds between 25 mph and 70 mph (or the vehicles' maximum speed if it is lower than this), the indicated speed must not exceed 110% of the actual speed, plus 6.25 mph.
For example, if the vehicle is actually travelling at 50 mph, the speedometer must not show more than 61.25 mph or less than 50 mph.