I'm looking to buy a car but scared of the petrol/running costs?

BMW 1 series, 5 doors hatchback, 2005, 1.6 litre engine, petrol, how much fuel roughly for full tank. How long would it last me if I do short trips like 4-5 miles everyday? Someone also told me that the petrol automatically goes on a bmw if not in use? Is that true? Will the fuel last me good time with the BMW like it did with my 1.25 litre ford fiesta lx 2004, petrol.

Fuel use will go up slightly but not a huge amount with bmw. No to second question.

Be ware bmw some of them need higher octane which run up fuel cost up had friend by one and didn't run good with out better grade fuel.doesn't use fuel parked. It will not get close to your fiesta if not have problem the your better kept it. Bmw maintenance is much higher not every body likes to work on them