I supplied my dealer with mobil 1 turbo diesel that I bought in a french hypermarket at 37 euros (under 25 pounds) for 6 litres so it actually worked out cheaper for the service as I was not charged for the Kia oil ! Dealer hadn't had it happen before but oblidged no problem and gave me the spare new oil back as well.( Note this on a Sedona)
I'll just add the 10k interval is high for a diesel but the car the Sedona replaced was a 110000 mile Fiat that ran mobil 1 from new and I serviced every 20000 (Bought it year old 9000 on clock) It has been well used (I have a wife and kids......) but has never been opened up just filters, plugs, cambelt, I've just had the HT leads + 1 Injector replaced but thats it. The oil is black allright but drains out with no sludge at all
I used to service Generators and will agree that you need to regulary change the oil ASWELL as keeping the air intake / filter clean and dont forget labouring a diesel is as bad as thrashing one
