In hot pursuit of the holy grail of modern motoring

Chris Dearden offers an economist's argument for purchasing a good-as-new Porsche 911 – and getting your money back

As a rational academic economist about to choose a new car, I might be expected to be looking at a Tata Nano if I'm worried about minimising my capital investment, or an 85 mpg Smart car if I'm more concerned about fuel economy, or a zero-emission Nissan Leaf if it's saving the environment that clinches the deal. But my prime concern is depreciation, or how to avoid it altogether, and because I'm an economist with soul, or maybe just with a mid-life crisis, I'm looking at a Porsche 911. And no, I don't mean a rebuild project, I mean a good-as-new, low-mileage 911 cabriolet for £25,000, or the price of the new Mondeo Titanium that my rational brain might have suggested. So let's consider this for a moment: which would we rather drive around in for a year? Both have their attractions, but on balance the Porsche probably gets the nod. And that is before you note that at the end of the year your £25,000 Mondeo will be worth £13,000, and your Porsche will be worth, well, £25,000.

I can sense your scepticism. What about insurance, fuel, service costs and new tyres, I hear you say. That's not a problem. Step back with me 10 months to a discussion some economist colleagues and I were having about the car-buying public's obsession with fuel economy when choosing a car. If we are looking at financial cost alone, the difference in fuel costs to the average 10,000-miles-a-year driver between a car that will do 40 mpg and one that will do 30 mpg is £500. In contrast, the difference in first-year depreciation costs between two different typical family hatchbacks can easily exceed £5,000. Now that figure is not one you will find in the small print at the bottom of the advertisement.

I rashly bet my colleagues I would be able to buy a Porsche 911 for the price of a new Mondeo, run it for a year, have no costs other than road tax, insurance and petrol, and sell it at the end of the year for what I paid for it. This would be the holy grail of motoring – a truly desirable car with no depreciation and low running costs. So how was I going to do this? Well if you study depreciation tables, you will see that the 911 takes a big depreciation hit in year one, then starts to level off, so that by about years four and five the depreciation can be negligible or even negative. But didn't I claim it would be a good-as-new low-mileage 911? I did, but this is where knowing your market is essential. There are a lot of abused 911s of this age available that will empty your wallet quicker than posting your bank details on the internet. But there are also examples that have only been used at weekends when the sun is shining, that have had full main-dealer cosseting, and are literally as new in all respects except price. As always, the challenge is finding them.

Now because the bet was for just a year's ownership, this affected the list of must-haves. A low-mileage convertible with a full main-dealer service history, no service due in the next year and tyres with at least 12,000 miles left in them. It would have to be immaculate visually and mechanically, with a good paint colour, and have an asking price that was at the bottom of the range for the year. Since we had been using the new Mondeo for comparison, £25,000 was set as the limit. And so the hunt began. Two facts rapidly became apparent: there are a lot of superficially immaculate but in reality horribly thrashed or crashed 911s waiting for the unwary. And there are a lot of nicely spoken men whose incomes come from matching those unwary buyers with their future nightmares. I decided that to keep the price low I would buy privately, and to minimise the risk I would get any likely contenders checked by a specialist. I drove a lot of miles, saw a lot of cars, and learned a lot about what I did not want.

After two months, I saw an advert with so little information I would not have bothered to chase it up if it had not been seven miles from my door in Hampshire. WX04MYV was an immaculate seal-grey metallic Carrera convertible, with Bose upgrade, sat-nav, virtually new tyres on upgraded alloys, and 15,000 miles on the clock. It had been serviced by Porsche Reading the week before, and the advisory worksheet was clear. It was five years old, but drove as if it had just come off the transporter from Stuttgart. After a check on its probity, £25,000 changed hands, and the drive home convinced me this was going to be a good year.

The English climate seemed determined to limit my early Porsche-driving experience. The weather in my part of the world made international news for its ferocity, and, even when the snow was cleared, learning to drive a 911 on icy roads did not seem sensible. But as spring approached, a planned visit to relatives in Austria for which we would normally have enlisted the help of Ryanair suddenly seemed more attractive in the 911, and an opportunity to visit the Porsche museum in Zuffenhausen on the way. On the way back, the weather intervened again, and a planned return over the Stelvio pass in Italy had to be cancelled when floods washed away part of the road. Luckily my navigator claimed she could find some equally exciting mountain passes that might be wet but were still in place. True to her word she worked out a route that zig-zagged us up and down passes in four countries in one day.

Back in England, discussion turned to the summer holiday. The trip to Austria had been ridiculously enjoyable, and that was in May in a storm, so how much better would it be in the warmth of August? A leisurely trip to the Pyrenees was planned, with a stop-off in the Dordogne. Anyone who tells you that touring in a sports car means restricting yourself to a spare pair of boxers and a toothbrush in the glove box has never tried it in a 911. The nose luggage compartment swallows a suitcase (and my laptop and walking boots). And each of the rear seats will hold a decent-sized overnight bag, or, as we discovered, a case of Monbazillac from the chateau near Bergerac. Three thousand comfortable, reliable miles were covered, and with the roof down the suntans were as good as they would have been from the beach.

So how has the year been so far? At the start, I was so in love I wanted to send it roses. Nine months on, and I still go to my garage just to stand and look. But I am trying to live by the principle that it needs to be driven regularly. I put a gallon of fuel in every 29 miles, and that is the limit of my spending. It burbles through towns, it howls on motorways, and the noise it made in the Alpine tunnels could have been written by Wagner. I drove it to the Goodwood Festival of Speed recently, and was offered £26,000 for it in the car park by a man who I suspect would have made his mark-up on it by the end of the weekend. I declined, because I have three months to go. Driving home, the depressing realisation hit me: in three months, I would have to say "yes" to a similar offer. I could always keep it, but are my pockets deep enough for long-term Porsche ownership? Probably not. So I guess it's on to the Mondeo. Or maybe, just maybe, I could start it all again, and look for the next depreciation-free Porsche for a year.