I have noticed that my vehicle seems to be lagging behind when driving at the poster speed limit. Other vehicles were catching up rapidly and stacking up behind me. I compared the indicated vehicle speed with two separate GPS devices and found the indicated speed was slower the the GPS indicated speed. At highway speed, 75 mph as indicated on the speedometer, the vehicle is traveling at 70 to 71 mph as reported be the GPS. I confirmed this by pacing another on vehicle with an accurate speedometer. I took my vehicle (2023 BMW X3 with 2218 miles on it) to the dealer for warranty service to address the issue for inaccurate speed reading on the speedometer. They provided me with a BMW service information bulletin (#B26 06 12 SI dated April 2012) which indicated that most speedometers have a tolerance of approximately 10% plus 2.5 mph, being necessary to compensate for negative tolerances in tire diameter and other outside factors. If a vehicle speedometer reads within that tolerance, no repairs should be attempted. This means that a vehicle traveling at highway speeds (75mph) as indicated on the vehicle-??s speedometer, the vehicle could be actually traveling at 65 mph. While traveling at 65 mph in a 75 mph speed zone in legal, it is not really safe and leads to unsafe traffic slow downs and possibly road rage incidents. I questioned the impact of the -??speed advance-?? on the total actual mileage the odometer, along with the computed MPG performance of the vehicle. Interesting enough, the service bulletin notes that the mileage does not incorporate any -??advance tolerances-?? yet it obtains its information from the same source as the speedometer. A 10% -??speed advance-?? (as identified) is unrealistic, unsafe, and unnecessary. Additionally, as related to tire diameter, as a tire wears and thus has a reduces circumference indicate speed becomes higher than actual speed, thus negating the need for the speedometer advance. I want an accurate speed reading while driving.

- Colorado Springs, CO, USA