It's not quite a Jaguar

[simont]

In other news, the car hassle now seems to be mostly sorted out. I've got a new (well, second-hand, but new to me) Polo to replace my defunct Clio; my insurance company have paid me a settlement that looked relatively plausible in terms of my own perusal of online price guides; I've given back the temporary hire car; all that's left now is for the insurers to sort out getting paid back by the other insurers, for which they don't need my help as far as I know. Phew.

Though I've been musing in the past few days that my methodology for choosing a car is wrong. (If you think it seems foolish to think about this just after I buy one, I wouldn't disagree, but better that than not thinking about it at all!) In the past my approach has been to think up a list of models that meet my basic requirements for size and price range and suchlike, then go and test-drive all of them; on some of the test drives I get a strong sense of wrongness, when it just doesn't behave the way I instinctively feel a car should, and then I go ‘warrgh!’ and decide not to buy that one.

The thing is, I got that same sense of wrongness the first time I got into the hire car, and actually it turned out I adjusted to that fine over a fortnight or so, to the point where the Polo now feels less right to me than it did in the test drive. I'm sure I'll readjust fine to the Polo, of course, but that's precisely my point: if that feeling of culture shock at an unfamiliar car is a basically transient issue, I shouldn't be basing buying decisions on it. What I want to be able to do is to distinguish the annoyances which are merely unfamiliarity from the ones that are genuinely annoying and will still be irritating me after a month, and I'm not sure if I can do that on a short test drive.

Or perhaps I should assume that any immediate annoyance is something I'll get used to eventually, and make my buying decisions solely on objectively measurable properties such as that model's statistical reliability, fuel consumption, likely TCO, and tedious things like that.

Comments

[gerald_duck]

That indicator feature sounds crappy. I bet it was coupled with one of those nasty "plipping" electronic reminders rather than the click of a relay? Rest assured I've tried plenty of vehicles made in the last two or three years which had traditional indicators.

Your new car sounds sensible. VW has a good reputation for reliability (good enough, in fact, that it's the marque I considered defecting to from Lexus) as well as more reasonable servicing costs than Audi. Are you intending to run it indefinitely, or do you have an eye on residual value? While fine for you, an engine that small might make it a little harder to shift on the second-hand market, so it might need to be traded in rather than sold privately. Similarly, if the red paintwork is non-metallic.

I realise, however, that I've never actually driven a VW. I've driven Audis and Seats, though, which amounts to much the same thing.

[simont]

My usual policy is to keep cars until they just become too unreliable or expensive to service (or, as it turns out, get unexpectedly destroyed), rather than trading in early so as to always have a relatively new one.

I sat down and did the maths once to work out the optimal policy for buying and replacing cars. Based on the assumptions that

1. a car's buying price decays exponentially with age
2. its selling price is a constant factor of its buying price at any given time
3. running costs are independent of the car so can be neglected
4. the sole optimisation goal is to minimise cost of ownership per unit time (i.e. (B-S)/T, if you buy for price B and sell after time T at price S)

my conclusion was that the optimal strategy was to decide how old a car you could possibly put up with, and always buy cars a fixed amount newer than that, where the length of time is given by a formula involving the time constant of the depreciation, the buying-to-selling price ratio, and the Lambert W function, and (after fitting some figures from Parkers to my simplistic pricing model) it worked out to about 3.5 years for the sorts of cars I was interested in. Of course you can't choose the age of the car you buy that precisely, so the second question is what to do with a car you've bought which is newer than that – and the answer is to still keep it until it's as old as you can put up with.

Of course every assumption in that list is shaky. I occasionally wonder about trying to come up with a better model which is still simple enough to analyse. I'd particularly like to be able to factor in the increase of maintenance cost as the car gets more decrepit, which I suspect would give rise to an objective minimum that didn't have that irritating dependency on personal preference; but I'm not sure where to get good figures for that.

[gerald_duck]

I think the most major complicating factor you've not modelled is mileage — that's very nearly as important as age in both determining a car's value and in its longevity and reliability.

To complicate matters, different people drive different amounts. I, for example — and I've not done the maths — reckon it makes sense to buy an older car with lower mileage, since that will weather 30,000 miles a year better than a young high-miler.

Running costs will be hugely variable between cars, based on their fuel economy, reliability, longevity (more precisely: tendency to become less reliable as they age and rack up miles) and original purchase price (a £10,000 secondhand BMW 7-series costs more to run than a £10,000 brand new Ford Ka). Unfortunately, two of those factors are subjective. But they matter: last year I happily bought a car that had done 130,000 miles. For a large-engined luxury saloon with a reputation for impeccable reliability, that makes sense, whereas I've known cars to be completely past it at 100,000 miles.