Do I need to tell my insurance company?

Yes. Tell your insurer. A remap is a modification to the vehicle and your policy almost certainly requires you to declare modifications.

Do not assume it will go unnoticed. A remap is detectable. Volkswagen Group has flagged modified vehicles on its online dealer system since 2013, and other manufacturers have their own checks. Anyone telling you a remap cannot be seen is selling you something.

The practical risk is not the premium, it is the claim. If you have not declared a modification and you need to claim, the insurer may reduce the settlement or refuse it altogether. That is a far bigger bill than any increase in your policy.

What to do

1. Ring your insurer or broker before you book, and ask what an ECU remap does to your premium.
2. Ask whether they want the stage and the claimed figures, and tell us if they do so we can put it in writing.
3. Once the work is done, confirm the modification is recorded on the policy and keep the confirmation.

Plenty of insurers take a sensible view of a software remap, particularly on a diesel tuned for economy. Some specialist brokers deal with modified cars every day. It is worth two phone calls.