I HAVE a 2004 Toyota Corolla that has an inaccurate odometer. After driving 100km, the odometer records 96km. I understand the speedo uses the same measurements to calculate speed. I have requested that it be repaired under warranty because there is always a risk of being caught for speeding. But Toyota advises that though it believes the speedo will be out to the same degree as the odometer, they will not repair it because it falls within the Australian Design Rules, which allow a 10 per cent discrepancy. My discrepancy is 4 per cent. Is Toyota's response reasonable?
YES, it is reasonable. A 4 per cent discrepancy is well within the allowable tolerance of plus or minus 10 per cent. Cars are assembled from thousands of parts, all of which have their own individual tolerances and these stack up as the car comes together. If the odometer is reading the way you describe, you should not have a problem. At 100km/h your average speed will actually be 96km/h. In other words, your speedo is optimistic, which is the case with most cars.