vauxhall zafira 2000 - CO2 Faults/ MOT failure- Help needed - louby76

Have had my 'v'reg zafira for 1 yr- just failed MOT on CO2 emissions- since getting the car have had to top up with oil every 600miles- was told this was ' a common fault' - now it seems to be a problem- garage have put some fluid in to flush the oil/engine and is in for a re-test on tues- he said next step would be either new pistons( which would mean splitting the engine etc - costing around £600 or a new /recon engine - again costing around £700 ) any advice would be greatly appreciated as feel utterly deflated with this news !thanks

vauxhall zafira 2000 - CO2 Faults/ MOT failure- Help needed - WellKnownSid

How many miles has the car done? What size engine? Petrol or Diesel? How much oil are you putting in every 600 miles? What were the exact emission readings? More information please.

vauxhall zafira 2000 - CO2 Faults/ MOT failure- Help needed - louby76

93000, 1.6v, Petrol, 1l every 600miles and I wasn't given the emission readings- I was told that they were too high and weren't registering on the reader- The garage then said to try a flush - he has put this in and I am to go back on Tues to re-test the emissions ( am I able to drive ( more than 10miles) with this fluid in ? ) thanks