23 mpg...really???

[Lux]

There must be something going awry with your calculations to produce 23 milers per American gallon. I would not use half-tanks as reference. Unless you have a voltmeter directly to the fuel level sender, half tank on the gauge is always interpretive.

I also live in Toronto and I get 600 - 650 km per tank, city only, air conditioning periodically used. City driving is usually where the Yaris should be faring better. Is your gearbox shifting late? It may need a relearn.

Originally Posted by Kaotic Lazagna

Are you using cheap gas, and is it possible that the gas station you're filling up in is still, some how, using winter blend gas (worse gas mileage with winter blend, even worse if using cheap gas).

All brands of petrol stations are supplied by the same handful of refineries.