An engine overhaul basically involves changing piston rings and probably the cylinder liner, if your engine has one. It may also involve changing other parts like journal bearings, oil seals etc.
In short, anything not up to spec insisde the engine is replaced.
Typically, overhauling is done when the engine is considered blown-by (blow by in the vernacular). In tagalog, kapag kumakain ng langis ang makina, kailangan nang i-overhaul :D
There is a shortcut method called the "TOp Overhaul", which does not require complete engine removal. Only the cylinder head is removed and only the piston rings are replaced. This is called the "Dukot" overhaul. I dont recommend this since some of the parts which need to be replaced are inside the engine block. Doble-gastos ang bagsak kung may kailangan din palitan sa loob.
paulo:: sorry pare ngayon lang ako naka reply... but tama si Juns. Punuin mo ng oil UP TO THE MAX LEVEL (only) of the dipstick. After a week or two, tignan mo kung gaano ang ibinaba nung level. Pag nasa minimum it means 1L na ang nakonsumo. Most dipsticks are calibrated to a max-min range of 1L.
If this happens, most likely blow-by na makina.
Walang way na maavoid ang overhaul. ang tanong lang ay kung KELAN. Of course, kung abusado yung makina, mas maaga ang overhaul.
mga sir, eh di ok pa naman yung kotse ko. kasi nababawasan yung langis pero ndi ganun kabilis. actually, mga ilang months na eh more more than halfway up pa from the min. binabantuan ko na lang nung natirang oil nung nagpachange oil ako. actually, mga 1 year pa nung pinaoverhaul ko.
ok lang yun pre. All engines consume oil, kaya lang, pag nasa kondisyon ang makina, hindi halata.
At the rate you described, mukhang tight pa naman yung engine mo. Like i said sa previous posts, pag 1L per week sa daily driven car, kandidato na sa O-Haul yun! :D