Sorry for the awfully delayed update.

I experimented first before I post some results. Before I sent my Optra 1.6LS for a reprogram over at Chevy North Edsa, I ran some tests first to see how gas just guzzles on this vehicle. I did my tests on city driving, all tests having had a near equal share of light to heavy traffic over at the metro. Tests were done from Muntinlupa up to Balintawak. What I found out was:

1. With airconditioning off, I could get at least 7km/liter. Average speed is around 60km/hr.
2. With airconditioning on, I could only get around 5-6km/liter. Same average speed.

This morning, I went to Chevy North Edsa for the reprogram. Yup, it's a bit too late. But running tests before really going to the casa was worth it for me.

Before I post on how it went, I'll answer two questions:

1. Why Chevy North Edsa?
Because a.) Chevy Alabang excuses, "There's no announcements yet by the main for reprogramming." and b.) GM Makati tells you, "Yes, we reprogram but we have to evaluate first if your vehicle is really in need of reprogramming. Plus, we're appointment-based so you have to tell us when you'll be visiting.". Compared to Chevy North Edsa, no questions asked. Just say you want to have your ECU reprogrammed with the Singapore prog. wait for a while, and done.

2. How much is the damage?
Since my car's still under warranty, it's free of charge. So feel free to drop by there anytime. Based on the warranty booklet, the warranty of the Optra is 3 years or 100,000kms. I think? You may feel free to correct me on this one.

Well, now the results. I sent my unit there by around 830am. They finished the reprogram by 10am. I even saw one of their service crew carrying the ECU reader upon getting off the vehicle. It shouldn;t have taken long but unfortunately Mr. Jeff (an SA) noticed that my engine kept stalling while he was parking the vehicle. So he told me that they'll clean the carburetor (not so sure) first. Still, free of charge. Spark plugs were intact. None were replaced (well, I actually changed my plugs to a Bosch Super 4 even before I sent the unit). Mr. Jeff explained to me that Mr. Castillo was just the one who recommended changing the spark plugs, but for him, it isn't necessary.

So, after getting my Optra back, I immediately ran my tests. And although this is just my first test (filled my fuel tank and I just can't refill 60 liters of gas and do 2 tests in a day now could I?), my computation is I averaged a 9.2km/liter with aircon on! This is terribly nice! =D

My car is all stock. None were changed in the engine area except for my spark plugs.

Hope this helps! Anyone else who had this done should post their results! like they said, "kanya-kanyang sasakyan, kanya-kanyang resulta". =D