was going down the highway the other day and passed one of those speed-detecting digital screens (I guess that's what they're called - right beside a speed limit sign) it showed my speed as 68mph but my speedo was reading exactly 70! Also when going 70 by the speedo, the average speed readout was 68mph. I'm one of those that hasn't put a tune in yet so it's all factory settings! Can the stealership correct this? I know this is not much error but I figure it's probably showing about 250 miles more than is actually on the car (currently 8300 miles). I was thinking that when I do get a tune I could set it for 3:73 gears while I am actually running 3:55's to make the speedo read slower than I'm actually going until I get those excess miles wiped off then re-calibrate it to 3:55. Thanx for any & all input

 

Those speed readout things normally over read actually, so yes, you might have an issue. Try to borrow a mobile gps unit to verify !