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Hi Everyone

SO i have my 1997 xk8 now for 3 months, despite some minor issues here and there this car has driven less the 35 miles in the last 4 years and i dont believe it has been serviced for the last 4 years, last service record was 3 K mile ago but 4 years is a long time.
Oil
The Oil topic has probably been talked to death but all the opinions are different on the grade of oil.

I dont know what grade was previously used , Sysnthetic/Semi synthetic / Mineral

What should be the best option for my 140K beauty.

Mobil 1 5w-30w
Castrol 5w-30w / 10w-40w

and is the leaky seals due to thinner oils just a myth because the engines are surely seald air tight , if there is a leak it would be big enough to leak either viscosity oil

Coolant

Now i also get the Low coolant message, is there a recommended coolant i can replace, i want to flush the system replace the coolant before i start to diagnose the float

Sticking with Jaguar's recommendations for engine oil is rather more important than it used to be in the 'good old days'. Devices like VVTs will only perform correctly and last well if the recommended specification oils are used. Gone are the days of increasing the viscosity of the oils used as mileage is added. I well recall selling straight 50 grade oil to keep down the oil consumption of engines with a mile or two under their belt - definitely not recommended for modern engines! Genuine Jaguar gaskets and sealants on these V8s provide excellent oil sealing and so tend not to leak apart from the occasional weep from a cam cover gasket.
Jaguar changed the type of antifreeze (sorry coolant) during the run of the 4 litre V8. However, the golden rule is to stick with whatever type of liquid is already in there. Mixing coolant types can be fatal to an engine's cooling. Adding modern coolants to good old antifreeze creates a gel-like substance which blocks radiators and other cooling passages. It's impossible to be sure how effective flushing a system has been so keep to the original coolant type to avoid trouble. Mike.