I find that a bit hard to believe. Someone in that family knew and took care of it sometimes.

The longest I've seen a used car go without an oil change was 40k miles and it was changed when it started making noise instantly on startup. That was basically 90k to 130k. Sure 0 to 40k would go a bit better.. but not 15 years of typical driving.

Between carbon blowby, gasoline dilution, oil burning at the rings/cylinder walls even if minimal, no car is making it 15 years if the person drives more than 5k miles a year IMO.