dk1

Odometer is very accurate. Speedometer is reading 5% high, probably on purpose.

Mbosko

I have known for ages that Audi specifically on purpose set their speedometers to read 5% higher (just so you don't get ticketed by chance). I live in Europe but probably the same is true for the US. It is difficult to track the specific difference by GPS as the GPS gets speed once a second (which is a looong time as speed goes). If you try to maintain a steady speed, you should be able to see the 5% difference between the GPS and the speedometer.

I have never hear the odometer being purposefully set to read more.

Scotty (UK)

All manufacturers have to ensure that they never under read the speed and hence they lean towards the conservative side. My B6 S4 was spot on even at 164mph (measured with laser timing beams)

Moviela

My experience has been that the speedometers are right on accurate. I have used both trackside and GPS measuring tools. My GPS is a simple Garmen, and it is easy to use to compare speed. It displays to one decimal place, and updates 300 times per second.

NJRoadFan

This is completely normal, my VW Jetta has the same exact behavior. What you may not know is that the speedometer inaccuracy isn't linearly consistent. The faster you go, the more inaccurate it gets (the percentage off increases the faster you go). ex: At 40mph it might read 1mph faster, at 100mph it may read roughly 6-7mph faster.

irenesbob

I am not being argumentative - I have found the same discrepencies with my 06 and 08 A4's, but:
My brother (an electronics expert PHD Physicist who worked for a major defense contractor as an engineer) has told me GPS systems are notoriously inaccurate for measuring land or over-the-road speed. Locationwise, they are dead on. The problem he says is that the GPS will calculate mph (or kph) by how long it takes you to get from point A to point B on the assumption that this is a straight line. He says it cannot account for curves. To use an example: exit 3 to exit 4 is 8 miles if you actually drive it going around all the curves. In a straight line it is only 7.6 miles. If it takes you 9 minutes to drive from one exit to the next the car's speedometer would say 53.33mph. The GPS would say 50.67 mph (a 5% difference). He could be wrong, since he retired about 3 years ago and there may have been product improvements since he & I had this discussion.
I still believe my Garmin, however - and I love how it converts to KPH when I drive up to Montreal - I live near NYC.

trucaliber

My GPS hud supposedly updates 5 times a second. And comparing it to my Pontiac's hardwired-HUD it's almost spot on. From 0-75 it displays my correct speed with maybe quarter of a second or less delay. I've tested it on straight aways, winding roads and even tree covered country roads. It seems very reliable everywhere accept downtown where buildings can block its signals. I'm not too concerned if my Audi's speedometer and odometer are separate from one another, but if they are tied together that is quite a few miscalculated miles.