I've noticed that my speedometer is approximately 4 or so mph fast as compared to GPS (i.e. speedo reads 80 and GPS 76). Have any of you noticed this? I assume this is a simple calibration that the dealership can handle?

2016 Jaguar XF Premier AWD

 

Did you put smaller tires? Also decrease the tires' diameters (wear and tear) will lead to the increase of angular speed = increase on speedo speed. With the smaller diameter the tires make more revolutions to cover the same distance.

 

Only by replacing speedometer but you're under warranty. Previous post is right on about tire diameter.

 

sn1peril, yes, there is an adjustment in the computer that will allow you to get the speedo a little more accurate. Granted, I would do a second check just to verify the GPS as the reading on a GPS can be altered due to how the GPS satellites are timed. I have had to learn more about the GPS satellites than I care to admit to and it is possible to alter the time of each satellite which can throw off speed and relative position. Granted, this is normally done in areas where GPS guided ammunition is being used. But, even having a satellite off by say a microsecond can have a big effect on things.

What I would tell you to do is to find a nice flat, straight road that you can travel on for say 5-10 miles. On this road, set your cruise at whatever speed you want and then note how many miles you travel, also noting the time it takes you to travel this distance. You can then take 3600 and multiply it by the number of miles that you traveled and then divide it by the number of seconds it took you to travel that distance. Normally 5 miles is a good distance to travel as you are getting any errors down to fairly small percentages. This will allow you to confirm what the GPS is saying and ensure that you are going to get the speedo corrected properly.

 

Learn something new every day. I'd like to see how this turns out for the OP if this is true.

 

Thanks all...stock tires as I bought the car with only 13k miles. Have had some validation by the roadside automated radar guns our friends in the police force put out but will further validate my gps reading.

D