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Discussion Starter #1
Yesterday did an experiment. 20 km of reasonably flat highway, light traffic. Set the cruise control to exactly 100 km/h (official limit here) on the clock. Then zeroed the average speed counter. This said 96 km/h from within a couple of seconds and stayed there for all the 20 km. The needle on the clock never moved off the 100 km/h tick.

Most cars have speedos that are 5-8% fast. If the computer kilometrage is accurate, this suggests the CT200h speedo is 4% fast. We have no measured kilometre marked on the roads here for manual checking. I'm aware that tyre wear, pressure, temperature etc. all play a role for both the speedo and the computer, so, at the best, any results must be an approximation.

Would you guys like to comment? Thanks!


BTW, I obtain 4.8 l/100 km highway and 4.4 l/100 km urban with 4.7 l/100 km mixed (averages) in hot weather (32-38°C).
 

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The only way your findings could hold is if your car gives the avg based on a different device than speedo which cannot be the case. Cruise is not dead on steady.
 

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Discussion Starter #4
Thanks for the replies.

But the computer does not depend on the speedo, possibly the other way round (and deliberately made to read fast). That is why I think that, if the computer data is correct, the speedo is 4% fast at 100 km/h.

"The Road Vehicles (Construction and Use) Regulations 1986, as amended, allows the use of speedometers that meet the requirements of EC Community Directive 75/443(97/39) or ECE Regulations 39. Both the EC Directive and the ECE Regulation lay down accuracy requirements to be applied at the time of vehicle approval for speedometers. These requirements are that the indicated speed must not be more than 10 per cent of the true speed plus 4km/h (2.5 mph)." "In production, however, a slightly different tolerance of 5 per cent plus 10 km/h (6 mph) is applied" "The requirements are also that the indicated speed must never be less than the true speed. A vehicle meeting these requirements would not be able to travel at a greater speed than that shown on the speedometer and a driver could not, therefore, inadvertently exceed speed restrictions.

I should imagine similar regulations exist in most countries.
 

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Both readings come from the same device/source. If you are saying your analog gauge shows fast that could be but I checked mine with my GPS and was ok. I wonder what others experience has been? I remember mine was off here and there by one mile but not all the time.
 

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Could this have anything to do with the fact that when I fill up my car I consistently get .2 l/100km lower than the car indicates on its computer? (I use the Gascubby app for the iPhone.) So when I fill up and the car says I was getting 5.0 l/100km, the calculated mileage is 5.2. Could this have something to do with the speedo being off a bit?
 

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My speed is usually 3-4% slower when measured by my iPhone than the speedo.
 

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I've noticed my speedo is about 1-2 MPH slower then what my phone gps says I doing.
 

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Mine seems faster. Both my 2011 CT and my wife's 2007 Prius are both about 2 mph faster. That is, if the car says 70, my GPS says 68.
 

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Mine seems faster. Both my 2011 CT and my wife's 2007 Prius are both about 2 mph faster. That is, if the car says 70, my GPS says 68.
Using my portable GPS, my CT's speedometer registers 2 mphs faster as well.
 
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