I was using Shell Helix Ultra 5W-40, which is supposed to be recommended by Ferrari and Porsche. Costs a fortune too.

Well one quick thing about the petrol that was put in at the start of the cars life was it just the wrong grade or did the put disel in and it was suppose to be regular un-leaded. Putting the wronf fuel can kill a engine or excell the death of it. I would try that angle with the lease and put the blame back on the dealer.

And 5w-40 seems a little low I would have thought 10w-30 for a warmer area of the world. Here in Canada in the dead of winter we use 5w-30.

With Mack attack on that one ... A 15/40 is more than fine but then again I have never owned a sports car :D But a 5/40 would not harm the engine in any way.

Regarding the rebuild Memnoch I would seriously get a quote on it... unless the engine is blown up as in hitting a land mine then the garage is taking the piss.

Personaly I would have taken legal advice as soon as they said the warranty was in breach, I'd have started at personal leveled at the mamager and worked my way up the company..

But I'm just spitefull.

You've got record of past problems with the vehical and records showing exsessive oil use..

find out what's the most you can sting them for then add emotional destress and loss of use of the vehical all the little things you'd not normaly think about.. At the end of the day you want the vehical fixed, yourself absolved of blame and all the costs incurred by this little escapade covered.

5w/40 is pretty light, shouldn't do any real harm though, better for your engine on a cold day/starting the engine from cold.
Personally I use 20w/40, but my car is burning a bit of oil so i'm thinking i'll move to 60w.
What did the manual say about the oil weight?