Hi Helen,

OK, a couple of things here to note. First off, I think you actually have a 1.4-litre engine as Opel hasn't made an Astra with a petrol 1.2 for several decades. Your total fuel tank capacity is 52 litres and at the official combined consumption figure of 7.5 litres per 100km, you'll burn through that in 693km, assuming you went from utterly brimmed to totally dry. 

The fact that you reckon you're getting 552km on a tank suggests that you're not achieving the official rated consumption figure, which to be honest isn't a surprise - few cars do in daily driving - and 140km in the difference is a bit steep, but not beyond the bounds of what we'd see on new cars. 

There are a few ways you can get better mileage though. Take any excess weight out of the car for a start. If you've got boxes of stuff lying in the boot or anything like that, take them out. 

Then check your tyres - are they in good nick and at the correct pressure? Wrong tyre pressures can murder your fuel consumption. 

Finally, what about the engine? Serviced recently? What about items like the air filter and oil filter? Fresh, new ones of those can make a difference and a full service can be a big help if you're trying to get your consumption down.