Should I keep? Or should I sawp?!?

[green A8]

Thanks for that info, I'll pass it along. I think the 4.0 that's being considered is a 55 plate as I seem to remember being told that it was in the lower VED banding. The car is a 40,000 miled one owner beast with FASH. No sign of an autobox service in the service book though. I thought they were supposed to get an oil/filter change at 40K?

[EG-4.0TDI]

Sounds like the right sort of territory. Worth checking the service intervals in the FASH - ie whether there were any huge intervals. Hopefully with only 40k in nine years, it will have been engine oil changed at relatively low mileage intervals which is supposedly much better for the chain drive. The gearbox is 'sealed for life' hence no published service interval for them although that should probably read 'sealed for shorter life'!

[Micha_elD]

You'd also have to factor in the cost of the swap, people will often focus on fuel costs because they are reminded of them each time they fill up, but I've lost about £25,000 on my A8 in the 7 years since I bought it, and spent £11,245 on petrol. If I'd had a diesel, I could have saved 20%, say, £2,250. For the guy that had the car for its first 18months, he had lost £45,000, but he was a director of Barclays, so he probably didn't notice.

Put this another way, every time I spend £100 filling the tank, I should put £220 in an envelope to cover the depreciation.

Overall,fuel costs don't seem to be much of a difference, and given the additional servicing costs of the diesel, I'd definitely pay the little bit extra to have a quiet, silky smooth petrol engine.

For your mum, the HM Revenue and Customs will effectively pay at least a third of her petrol costs for business mileage, so she won't care as much as you