Don't get the impression that diesels are no good at all. They're still a better bet on balance if your mileage is higher than about 15,000 pa: but avoid them if you do a lot of short journeys.

Also if you're buying secondhand, avoid high-mileage diesels except those with engines of older design (like the VW Group 1.9 TDI). Newer designs have appendages like DPF and DMF which can fail expensivey at high mileages.

I don't know how big a car you want or what your budget is, but there are some very efficient smaller petrol engines about now which are worth a look if you're buying new or nearly-new.

Edit - now I've seen your other thread! If your budget is below £2,000 I stringly suggest a petrol. The Toyota Corolla, Honda Civic, Nissan Almera and Mazda 6 are all very durable.

But ultimately it's condition rather than make and model that should be the deciding factors for you at this price range.

Edited by Avant on 24/01/2012 at 23:24

You don't say what age of Mondeos or Focii you're looking at.

The 2.0TDCI in the Mondeo doesn't have a DPF, but some have issues with DMF. They're not wonderful for fuel economy either, especially in 130hp guise. The 115hp version seems better on fuel, and kinder to DMFs. Mk4 Mondeo is 1.8TDCI and a new 2.0TDCI.

Focus, well, Mk1 Focii all use the old 1.8TDCI, which is the tarted up 1.8TD from the Escort. Good enough engine. Mk2 Focus uses either the 2.0TDCI from the Mondeo, the same old 1.8TDCI tweaked, and the newest of the lot, the 1.6TDCI. The 1.8TDCI is 115hp (no DPF), the 2.0TDCI is 130hp (DPF), and the 1.6TDCI is available with 90hp (no DPF) and 110hp (Eyols DPF). Avoid the 90hp 1.6TDCI, it's pretty miserable and doesn't get much better economy than the 110hp version.

Personally, I'd still go for the 1.8TDCI in 115hp form, I think it's the most solid engine, having been in Ford's lineup for decades. Either than or a 1.6TDCI with the DPF removed and mapped out.