madaming pwedeng reasons why makonsumo ng langis ang kotse... pwedeng may leak... pwedeng may matigas na gaskets, pwede din sa bandang transmission may problem din, pwede dingbaluktot na mga barbula... etc...

general overhaul ba ang ginawa last year? whether it's a general or a top overhaul you should track ung mga pinalitang piyesa. try to first check if walang tagas by having a decent engine wash (those who really know how to do it without damaging your electrical components- alternator, distributor, and everything else electrical- ung mga male and female receptacles pwede ding mapasukan ng tubig and masira), and see if may tagas.

if wala, it can be the transmission or the engine parts already.

HTH