Gas/Diesel Price Map in the Philippines

I don't track gas prices much.  The vehicles I've used for the past two years all use diesel.  I've observed that the cheapest diesel prices change from location to location.  At the start of last year, prices by the coastal road and near the NAIA airport seem the cheapest.  Now, they're more expensive.  A few months ago, it seemed to me that gas prices in Pampanga (and probably in other provinces) are cheaper than in Manila.  Recently, I've noticed that gas prices in NLEX are cheaper than most in Metro Manila, when before, it's the exact opposite.  My favorite gas stations never last.
So maybe an updated map of diesel and gas prices would help.  That way, map users can reward gas stations that offer cheaper prices, and help in the fight against uncompetitive price control.  Today, I found out there's already an attempt to do just that: http://www.tipidgas.com/.  There's much that can be improved on the user interface front, but the gist of it, a map of gas stations with documented prices, is there.

I can't say whether it's successful or not.  I've only given it a cursory check and it seems some (if not most) prices are a few months old already.  Oh well.  Such a project can't easily be covered by just one person listing all the prices of gas stations he or she passes by.  This project demands community support, much in the same way www.openstreetmap.com was made.  Willing contributors must update gas prices they encounter frequently.  People who will make use of the website, by then going to cheaper gas stations, can update the prices and date of validity as they encounter changes.  It's a lot of work for a lot of people.  Is it worth it?

It sounds like a more practical approach to getting cheaper gas prices is to gas up to full tank once you've found the cheapest gas or diesel among a set number of stations or locality.  You don't have to wait for an empty tank to start buying gas -- by then, you won't have much opportunity to shop around, and you lose choice of where you can gas up.  There's no guarantee of getting the cheapest rates, but at least you're guaranteed of not getting the other end of the stick.