Quote Originally Posted by bail View Post
Na observe ko after changing my oil from 20w50 to 10w40 and also from bosch platinum spark plugs to OEM spark plugs, fuel consumption ko naging 5km/liter na lang. bago din naman ang air filter. car is 1997 corolla 1.6 gli with 123k mileage. Ano kaya ang problem?





With that mileage, the timing belt should have been replaced already. If it was not, chances are the timing belt has stretched causing late valve timing or the timing belt has skipped a tooth or two. Verify correct cam timing using a vacuum gauge. The vacuum should be between 17-21 in.Hg. preferably around 21 in.Hg at idle speed.

There is a possibility that the exhaust is partially restricted. The exhaust back pressure should not exceed 1psig measured at the oxygen sensor mounting.