I am looking to buy a second-hand car for my daily commute to work, which is around 60 miles per day of almost all motorway and A road driving. I have around £6-£7k to spend and was looking at something up to 3 years old. Obviously the most fuel-efficient cars are superminis and I was wondering if these are still as efficient at motorway speeds due to their smaller engines or whether something like a Ford Focus would be a better purchase? I am also plagued by the diesel v/s petrol question. Any ideas on a good purchase?