For the last seven years, September has been the key month for new car registrations following the introduction of the new style number plates. However this year the credit crunch looks set to take its toll on the number of new 58 plate registrations. With many putting the decision to buy a new car on the back burner, HPI offers some words of wisdom on used cars that will not only be more cost effective to run and environmentally friendly, but are most likely to hold their value.“Those keen to trade in their current vehicle for something else need to think carefully about their next purchase,” says Martin Keighley, HPI's used car valuation's expert*. “It is really important that consumers think about a car’s potential to depreciate before parting with their cash. Winners will be anything small and economical, with low CO2 ratings. My top picks include the Toyota Aygo (and its sister cars, Citroen C1 and Peugeot 107), Fiat 500 and Hyundai i10. Image conscious drivers will plump for the Mini, which is a bullet-proof buy as long as they stay away from the high end models.” HPI’s valuation expert goes on to recommend that when it comes to medium sized cars, the latest eco-friendly models will also win the day. The VW Golf Bluemotion, Audi A3 1.9 economy models and Seat Leon 1.9 Ecomotive are all sound investments in terms of low running costs and hold their values.Keighley concludes, “With money tight, many drivers have been panicked into downsizing their vehicles in a bid to cut their fuel and Vehicle Excise Duty bills. As a result, the list of undersirables is growing with large petrol engines top of the no-no pile. I would even consider that the 2.0 is too large in 4x4, people carriers or Vauxhall Vectra-sized models, these days. However, as times get tougher, we need to be aware of all the factors that impact on vehicle values. Although common sense has a lot to do with buying decisions, don’t forget that desirability can also rule the day.”HPI Valuations’ Top Ten Sound Investments1 Mini 2 Citroen C1/Peugeot 107/Toyota Aygo 3 Fiat 500 4 Hyundai i10 5 Audi A3 Diesel models 6 BMW 1 Series Efficient Dynamics 7 Ford Focus diesel models 8 VW Polo 9 VW Golf Bluemotion 10 Seat Leon 1.9 Ecomotive