Don't know what will happen if you use a Synthetic, But for the Flush- Just ensure that you buy a decent OWS or STP Flush Treatment- 1 can is good enough for 4-5 ltrs of Engine Oil, How much does a Qualis take-calculate it accordingly.
City motors as Opera House sells it for Rs.650/liter. But that extra 20/liter may be ok if you live on the other side of town.
is this the city motor co. i saw this in a tiny lane near central plaza. the whole lane was full of car shops. this is the shop you were talking about right? i will be going there on saturday to pick up oil for my getz.