It's an "old-school" engine, if Kia say 10w-40 then use that, 5w-40 or 0w-40 - all the same warmed up but thinner when cold so circulates quicker. Find out what ACEA rating Kia specify and stick to that rigidly.

Don't use a -30 oil, that's fine for modern low tolerance engines but not if -40 was required new.

Low SAPS oil is ok on cars without DPF (it's a requirement if they do have one) but focus on the other aspects first

Thanks for the advice RT and Gordonbennet,

I realised I had made a mistake, It was actually 10w30 B4 that Kia call for so I guess the Merc oil would be ok to use.

On the ASDA website, their own brand oils are on offer at the moment, and they do a Ford specification 5w30 fully synthetic, £15 (down from £22) for 5 litres. The only thing I can see wrong with this oil is that it is a B5 fuel economy oil whereas Kia are calling for B4.

My understanding from a few websites and forums is that B5 is a slightly lower viscosity oil which may not provide adequate protection.

I imagine that it is still probably better for the engine than the 6 year old oil is at the moment though!

Millers Trident 5w40 A3/B4 £80 for 25litres.

I'm always sceptical about buying oil on Ebay unless it's a reputable seller as there have been many cases of 'fake' oil being sold and who know what might actually be in that bottle?

Edited by Wackyracer on 09/04/2016 at 11:43