I remember computing the fuel efficiency vs. upfront cost of the Wigo and the Mirage in another thread before.
Anyway, I'll give it another go, with the ff. assumptions:
1. Wigo 1.0G AT SRP - 534k
2. Mirage 1.2 GLS CVT SRP - 648k
3. Wigo 1.0G AT FC (90% city, 10% highway) - 11.98 km/L*
4. Mirage 1.2 GLS CVT FC (90% city, 10% highway) - 14.82 km/L*
5. Gasoline price at Php 52.00/L
* according to James Deakin. Unless you're better than Deakin, I'll take his numbers as reliable
Even if you travel 10,000 kilometers per year, it will still take you 14 years to offset the SRP difference of the Wigo and Mirage, even if the Mirage is more economical. That doesn't include the difference in maintenance cost, but it should be minimal.
Lowering that to 7,000 km per year increases the time to 18 years before a Mirage becomes more economical.
My point is - if you want to have the lowest running cost for a brand new car, get a Wigo. However, I think the Mirage is the better car overall so it's worth the extra cash.
I also wanna add that if you want the lowest running cost (incl. upfront payment), cheapest way is to go secondhand and get a gen 1 Vios. Even with more maintenance, it'll still be cheaper than going brand new. Also has more power and space compared to the Wigo.