Timing belt versus timing chain is a cost issue, but ont necessarily a deciding one if you are keeping a vehcile 10-12 years. Assuming you cover 100K in that time you are going to be changing the timing belt once on most cars in some cases twice. The newer Highly Nitrile saturated belts on such cars as the lynx engine in the latest ford 1.8 diesels are quoting 150 K or 10 years, the HDi Peugeot engines have been on 100K or 10 year intervals. VW replacement is vehicle and engine specific but averages around 4 years (audi often being 5 even though they are basically the same engine). At our garage we would normally replace the cambelt according to autodata for that particular vehicle and replace also the tensioner, idler pulleys etc and the water pump if its driven off the cambelt. Typically on say a 2.0 TDi VW with genuine parts fitted you are looking around £ 300-350 fitted. Whether to buy a car simply because it has a cambelt or chain should not be a major decider. In the above example you are talking about a tank of fuel extra per year over a 5 year period, versus a far greater saving you may make between two vehicles (chain and cambelt ) in other areas. Other replies have already eluded to the dual mass flywheel which typically last as long as or sometines slightly less than the life of a clutch. In any case we have yet to change a clutch at the garage on a car fitted with a DMF and not change the DMF at the same time. Here parts costs can be outrageous. A Full clutch kit might be £120-150 (Gen parts) with say £200-£300 to fit (depending on the car) but a DMF for the same vehicle could be £ 400-800. Making a clutch repair £ 800-1200. On a 10 year old car its often the value of the vehicle!! Diesel technology has improved tremendously in the last 10 -15 years. So has the cost of the fuel system with older diesel fuel pumps being £ 300-400 and the newer ultra HP common rail pumps being £ 500-3000 each. Injectors similarly can be anything from £ 100-600 each fitted meaning a 7-8 year old 330d BMW can soon swallow £ 1000+ on a fuel injection issue when you include diagnostics and fitting etc. DPF's are away for manufacturers to to get better emissions from their vehicles. They are effectively a soot filter. The soot builds up on the filter and periodically needs to be burned off. The engine does this on some vehicles by injecting a tiny amount of fuel onto the exhaust cycle of the firing sequence and effectively burns the soot off. To do this the engine needs to be fully up to temperature and needs to be running a reasonably high engine revs for a sustained burn period (Rep driving along the M1 is fine versus Auntie Flo popping to the shops not fine). DPF equipped vehciles also require very sepcific low SAPS oils that are typically charged out at 2-3 times the cost of ordinary equivalent synthetic oils. If you are going to be travelling less than 10K per year then defintiely petrol over the equivalent diesel. If you are keeping the vehicle 10-12 years the resale value of a diesel to a petrol is irrelavent and the running costs more significant. Most mid sized 1.5-2.5L Diesel engines now have a DMF whilst most petrol engines of a similar size dont as they dont transmit as much torque shunt to the transmisiion at take up speeds as an equivalent diesel. Try all the contenders in your price range. Dont be frightened to buy 2nd hand aslong as you buy from a reputable source and try and avoid ex lease vehicles. (they come with full service history) but lease companies are notorious for spending as little as possible on the vehicles. Typically in 40,000 miles they might have had two oil changes and the wheels have probably never been off the car other than in a tyre house. If you use a local garage rather than a main agent talk to them about what they recommend.