Does the car's ECU know the actual mileage?

[Leicesterdave]

My car has had a change of speedo and it's reading 25000 miles less than it's done. I'd like to obviously add the real miles it's done. Does anything in the car retain the car's true mileage?

[TheEnd]

Not usually in the engine ECU, but there will be other components that will hold it, and it is often held in the car keys too.

[Leicesterdave]

TheEnd said:

Not usually in the engine ECU, but there will be other components that will hold it, and it is often held in the car keys too.

How do I go about it? Main dealer?

[Kiltox]

I know that Vauxhalls store it somewhere that can be read with a Tech2 (I assume in the ECU).

Might be a job for an independent specialist though, main dealers tend not to be very good at something out of the ordinary

[TheEnd]

Best bet is a "mileage correction" place, they should be able to set the instrument cluster to whatever is needed.