Synthetic oil is 'safe' for all engines, although there are alot of
old wives' tales about. In fact, anyone who runs a relatively modern,
high performance car should be using it as a matter of course.
Obviously it doesn't make a lot of sense from an economic point of
view to run expensive modern synthetic oils in loose old engines which
burn or leak a lot, but I'm sure that is not the case here.

David Betts (davidb@motorsport.org.uk)
The Classic Car Gallery: http://www.ofoto.com/I.jsp?m=17830847103&n=398038677

On the owner's manual, as well as the keyless entry, your best bet is to go
to www.jag-lovers.org and research the XJS forum.  Often, you will find
owners of XJSs with sources for manuals  and certainly information regarding
keyless entry. Whilst there, you should download Kirby Palm's book about the
XJS  http://www.jag-lovers.org/xj-s/book/Jaguar.html     Many owners have
canned the manuals into electronic form.  Unfortunately, mine are all for
older Jags and different models from yours.

As for synthetic oil.  It is certainly "safe" for the 4.0 liter Jaguar
engine.  The question goes to the number of miles on the engine and the
number of miles you will be driving the car in the future.  I would not
think of putting synthetic in my XJ40 with 210,000 miles or any of my older
saloons.   I did not hesitate to recommend that my friend put synthetic into
his 2001 XJR  which he literally only drives to church and the car wash on
Sundays.

Putting synthetic in your XJS will certainly not hurt the car.  I am not
sure, however of the benefits versus the cost, however.

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