Does anyone know the answer to this ?

JohnM20

My car, like most others I guess, has a speedo that reads slightly high, typically 33 when actually doing 30mph. I understand the reason for this but do all the other computer information readings also suffer from the figures being out a bit, average speed,
average fuel etc and, if so, would they be out by the same percentage as the speedo? I've pondered this for some time and would really like to know the answer.