What if you're a car person (who has been doing ALL of the work on your vehicles yourself for decades)? You're not going to have those receipts when it's not done in a shop right? Especially little things like oil that most people could physically do.

In the event of an accident, you're still gonna need quotes from an independent third party, and the ODO will be on the paperwork. And the insurance company can still say "no, you're not allowed to repair it yourself." Which they likely will, cause fraud.

As for the service stuff, you'd still potentially have receipts (or CC transactions) for all the oil and filters and stuff you've allegedly bought along the way when you "did it all yourself."

You're missing the forest for the trees though. The burden of proof will be on you to prove you weren't lying about your mileage. The insurance company isn't obligated to believe you.

If you've been reporting low mileage for several years and now in 2022 you're claiming the +50k mileage difference between your estimates and the ODO reading was all accrued in under 12 months, they're going to ask you to account for the additional 1,000-3,000 hours you put behind the wheel this year.....and that's if you got a full year since your last contract. Renewed 3 months ago? Yeah, obvious scam is obvious.