I had a bit of spare and thought it would be interesting to see just how much error there is on an old Civic EG gauge cluster. I tested the main gauges at a few points to see whether or not it's a fixed error or a percentage and found that in my case it's around 4-5% high.

For those interested in how to test the cluster, connect a function generator (0-12V square wave) to the screw terminals in the back along with power and ground and start by setting the frequency between 10-200Hz. Also, as the frequency increases there is a point where the needle will "reset" itself and start sweeping through the range again.