www.jec.org.uk

For all intents and purpose my 6.0 XJR-S is really a 5.3 with some frilly bits. So what oil should I be running? There's a wide band of grades in the book for the kind of UK temperatures we have, and it's currently done only a few miles on shell helix ultra 5w40, which isn't the right grade for this country's weather from what the manual says so I want to change it now.

Should the oil be fully synthetic I assume? I mainly ask as I keep a very big stock of 10w40 semi synthetic for my two other cars which I change regularly, and being lazy, would like to use the same, but only want to use the best for the car.

I take the view that the basic engine is quite old and designed decades before some of these fancier oils were thought of so I just use a semi-synthetic 20/50. A thinner grade like 10/40 just encourages the leaks!
I also change it frequently.
regards
David

Try the following link.
It doesn't specify a particular one for your model but it does suggest that you call their technical helpline; let me know what they say as I want to change mine soon!
http://www.morrislubricants.co.uk/lubri ... efault.asp

I've been using Morris's 10W 50 semi synthetic very satisfactorily in my 1991 5.3; doesn't consume much between changes, stays pretty clean for much longer than the old organic oils.

I always use mineral oil...20/50...as I read synthetic can cause seal leaks, I don't know about semi-synthetic..

I use 20/50 mineral oil - have done for years.

They used to say, If a Jaguar has no oil leaks it has no oil !

Excellent thanks all!

I've just noticed how my XJR-S Supplement oil page varies from the standard book page. "Due to the high performance capability of the 6.0 litre V12 engine, Jaguar recommended that a suitable high performance synthetic engine oil which meets the specification requirements shown below should be used at all times..."

They recommend Castrol 5w50 or 10w60, as well as the standard oil chart that you probably all have. I'm probably going to have a go with the latter! Interesting as I wouldn't have thought there was that much difference.

Was looking in Wilco this morning. 5l containers of semi-synth 10/40 and 15/40 for £15. Fully Synth for £20

'Own brand', but It meets all the standards, Unless someone tells me its rubbish I think its worth a punt?

I have run with semi-synthetic and more recently, fully synthetic (Comma X-Flow Type G Fully Synthetic 5W40). I would agree that fully synthetic encourages more leaks so make sure that you don't have too many Some slight leakage is fine as this is my sub-frame rust prevention system