[quote=“LJPgeoman, post:1, topic:105388, full:true”] I asked the dealer service department and they asked if I had larger tires (they are the original tires) and at first they told me the speedometer can’t be recalibrated. .
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This is a big clue as to how clueless they are. Larger tires would result in the speedometer reading too low, not too high.
Mile markers are placed very accurately, and any small errors would average out. That’s why something like 10 miles is a good distance to use.
This post reminds me of the old saying, “A man with two watches is never sure what time it is”. 
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Even a broken clock has the right time twice a day.
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Each one is different. The one that is off the most says I’m going about 7 MPH slower than what my measured speed is. They are only used in construction zones in MD, and the construction in that area is done. I hope they fixed it before moving it to the next construction site.
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Thank you for telling me my expectations are totally unrealistic. Thank you more to all who tried to help me with suggestions.
The radar checks show I’m going slower than my speedometer indicates just like the cruise control speed indicator and GPS show.
Thanks for all the suggestions. I can easily live with the speedometer being off. I keep my new cars an average of about 15 years so I was more concerned that the odometer could show 1000’s of miles more on it than actual miles when it comes time to sell. I’m not even going to try and calculate the possible actual difference based on how many miles I drive, etc. I mainly wanted to know if the speedometer can be recalculated and I got my answer. The dealer at first told me no but I just took the car in for a recall and a different service manager told me they could check it - I have a year left on the warranty to decide if I want them to try and fix the problem.
The radar beam angle has to be directly in line with the direction you are moving for it to be accurate. Since the unit is positioned off to the side of the road, the radar pulse is hitting your car at an angle, so it will read lower than your actual speed. I think every vehicle I’ve ever owned, when I timed it using the mile marker method, I discovered the speedo read a little higher than the actual speed for some reason. It may be the car companies liability lawyers require that. They figure it is easier to explain to a jury if the vehicle’s speedo reads a little faster than the owner is actually moving, compared to it indicating the owner is moving at a safe speed, when in fact they are moving faster than expected.
[quote=“Renegade, post:24, topic:105388, full:true”]
Even a broken clock has the right time twice a day.
[/quote]Not a digital clock!
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The cruise control set speed that you see in the information display is the speed the PCM has calculated as the vehicle speed. The PCM sends this information to the instrument cluster for the speedometer display when the cruise is on or off.
It seems the speedometer display reads high, this may be intentional to allow for the variety of tires available on the car, the same size/different manufacture tire can have different diameters.
I am not familiar with your Ford but my experience with other vehicles I can calibrate each gauge in the cluster with a scan tool. Your dealer may not offer to recalibrate your gauges if they are within a reasonable degree of accuracy, the technician probably won’t get paid for his effort. You need to have a good relationship with your service advisor to receive special attention.
@cdaquila Hey Carolyn, look at the post above this.