A-Best: thats disgraceful, my 1994 renault clio williams - 2litre 16v 182bhp - which has lots of modifications probably has around the same MPG for normal driving, something is up with the Polo, i wouldnt think a blowing exhaust would cause such bad MPG, when i had a 2litre diesel golf GT TDI 2008 that would give me 40+MPG at steady driving, you should be getting around 70MPG for average drving!