My car has 130k on the clock i havent had to replace the clutch, brakes or anything major and mine was alot less then 5k.
look more for common faults, stone chips and accident damage u cant change what fuels been used and you will never know for sure either but if the cars reached over 100k with good service history and still runs great then i wouldnt be too worried.
Dont let people put u off buy a car with good service history and low owners .
Mileage isnt a guideline on how well the cars driven or maintained either. To me it means its been sat for a long time and hardly used or not been able to afford to drive/maintain it.
Test drive a few cars, pick the best car for ur budget then buy it use the correct fuel and enjoy it.