Hi Ashling,
Heres a few figures to have a think about assuming the merc was a CLK 200. This figures are all approximate going on combined MPG figures from the internet.
The type of driving you do has a huge impact on these, city driving will be a lot worse, country driving a little better.
In reality car makes fuel figures should be taken with a pinch of salt but it does show you that there will be a big differance between cars.
Beetle is just a golf with a fancy body, is it worth the extra over a normal golf? Most people think not. Personally I would buy a year newer golf if going down that route but then I'm a man! Golf or beetle diesel will do about 200 miles more per tank than your Ka and cost about 20 more to fill.
Mercedes will have higher running costs apart from the fuel, and a full service history will be vital. Make sure there are receipts, not just the book stamped. That goes for any car actually. So merc would cost you about 30 quid more per week to do the same sort of miles as your Ka.
Hope that helps a bit!
[FONT="]Mercedes CLK200 has 62 litre tank.
This will cost approx €74 to fill at €1.19 per litre petrol
Combined MPG is 31.7 so about range approx 420 miles per tank
VW Beetle 1.9TDI has 55 litre tank.
This will cost approx €69 to fill at €1.25 per litre Diesel
Combined MPG is 53 so range approx 640 miles per tank
Ford Ka has 40 litre tank
This will cost approx €47 to fill at €1.19 per litre petrol
Combined MPG is 44 so range approx 430 miles per tank[/FONT]