High mileage does not necessarily require major repairs, while low mileage does not guarantee that you will not need one.
Excessive oil consumption indicates that attention should be paid to the piston rings, valve seals and/or valve guides. Before assuming that the rings and/or guides are bad, make sure there are no leaks.
Check the oil pressure with the sensor installed in the oil pressure check unit and compare it with the value specified in the specification.
If it is too low, the bearings and/or oil pump may be worn out. Loss of power, noticeable valve noise, and high oil and fuel consumption may also indicate the need for a major overhaul, especially if all of these problems are present at the same time.
During the overhaul, the pistons are removed, and the holes are drilled and honed. New pistons are required to enlarge the holes. The main bearing, the upper connecting rod head bearing and the camshaft bearings are usually replaced with new ones; if necessary, the crankshaft is ground to restore the journal surfaces. The valves are also serviced if their condition is noticeably worse than other units. During an engine overhaul, other units should also be overhauled - the generator, starter, distributor.
Note: Unreliable elements of the cooling system - hoses, drive belts, thermostat, water pump should be replaced with new ones during engine overhaul. The radiator should be carefully checked. It is not recommended to repair the oil pump (except 3.8L) - a new one should be installed during engine overhaul.