Hello, My 95 Civic ESi (Philippine domestic version) is similar to the U.S. EX version, I think. It has a PH16 engine (PGM-FI, 16Valve, 1.6Li, SOHC non-vtec, ECU code P27) but it has no oxygen sensor! This is common knowledge here, and there is a plug where the sensor should be. My question is, is this a great disadvantage in terms of mileage? Average mileage for civics here is 18 to 24 MPG (~8-10km/liter). Why did Honda do this? Is the ECU always running in open loop mode? Can we somehow buy an O2 sensor and put it in, and if so, will this buy us much MPG-wise? Thanks so much in advance, I hope someone can help.