I have a 2005 S80 with approx. 53K. The Trip Computer works fine as far as Driving distance on current fuel reserve; Average fuel consumption; current fuel consumption; (note when I take reading after filling the gas tank from the trip odometer) , the MPG given as average fuel consumption never varies more than 0.2 mpg) However the Average Speed always read 34 mph!! THis does worry me but I would like to know why this one reading should be the odd one out, as all the rest are accurate. Needless to say I don't drive at 34 mph, although at the moment most of my driving is 80% city, and 20% highway.

 

Mine is around 26 MPH Average Speed. I don't think there is anything necessarily wrong with it because I look at all the stop and go, waiting at lights, etc. Most of the speed limits outside the 4 miles on the highway to my house are under 40 MPH.

 

i think it is ok, mine shows 28 at this moment.