I think that its all down to personal circumstances, I don't
think anyone is knocking the choice to run an old car. It would be immenseley hypocritical in my case to do so, given I have for over 15yrs, up until last year, never run a car under about 10yrs old. However, the balance of needs and wants changes over time. For me, the next step up in career means I'll:
a) have very little headspace for anything else,
b) be doing a lot of miles
c) be taking a substantial car allowance (doesn't look good receiving £5-10k/yr to run a £500 car)
d) be meeting with a number of board-level types on a regular basis
Now, none of these things preclude running an old car per se. However they do shift the balance away from it towards something new or new-ish.
The cost of running a new V60 over 100k & 4yrs is about £5000 + 48*350 = 21,800 + 12,150 in diesel = £33,950, a "nearly new" s80 on a bank loan would be £16,700 + 11,350 + 1800 (servicing) + 880 (volvo warranty) = £30,730 (assuming a conservative residual of £3k). Running my omega would mean £19,450 in fuel, plus servicing and unexpected repairs at £150 p.a. (likely to be more in reality) = £20,050. So it will cost me about £10-14k over 3yrs, or £210-280 per month to run a new (or nearly new) car. That also assumes the most expensive of everything, full volvo warranty, main dealer servicing etc etc. And assuming nothing goes wrong with the Omega in that time (80-180k, probably a slightly optimistic assumption). In my judgement, this is a worthwhile cost.
Yes, I could LPG the omega, but am I realistically going to finish a 9-10hr day, drive 1.5hrs home and then go looking for LPG? Unlikely in my case. And the limited range would mean that every 1.5-2 days I'd be filling up. The diesel will go a full week in the summer, 4 days in the winter.
The starting premise is not, what is cheapest to run, as I suspect the answer would be a 406 diesel running on Farm Foods veg oil.
. The starting premise (for me) is that I want to run a newer car, for a lot of miles, thats auto, has acceptable performance (8s ish or less to 60, with decent mid-range shove). Within those boundaries, the V60/s60/S80 seems the best option.
For the record, my desmond auto has settled on 28mpg over the average tank. I can average 31-32 over a tank, but I'm left wanting to shoot myself.