it is really not the biggest issue. Jaguar recommended Castrol when the car was new. key is changing it often enough. low mileage and short trips means you are in severe service and should change the oil every six months. if you run synthetic with high base numbers, you can go the entire year on severe service. essentially synthetic can take a lot of abuse.

 

It's not really the synthetic brand that's important, but the spec. which is standard 5W30. I've noticed that the synthetic is still brown, not black, when I change it.

As our cars get older, we need to change the oil and filters more regularly depending on the environment and our use. In Bahrain it's 10degC-50degC ( yes that's 122degF in the summer... shade temperature) so I go for 0W40 here.

If you are really concerned about carbon build up, there are now Terraclean, or similar, specialists that run a special cycle of detergent fuel which cleans out the carbon deposits in the engine. The only problem is to find a local outlet. Mine is in Oman, so I would need to do a road trip (Bahrain-Saudi-United Arab Emirates-Oman).

 

HI mine is a 2001 4.0L sc, and jaguar spec is to use 5w30 Acea A1 or A3 i would think your 4.0L na should be the same spec (this is just my guess)
lots of 5w30 out there but you need to check its Acea A1 or A3 , iv just bought 7 litres of castrol edge 5w40 Acea c3 , NOTE it is C3 not A3 i dont know the difference between C3 and A3 but its going in the engine soon, it takes 6.5 litres for my oil change , next time im going for the castrol GTX 5w30 A1 semi synthetic which i think is the correct spec for my car and a lot cheaper than castrol edge also the castrol GTX is apparently made for the older higher mileage car ,hope this helps.

 

regarding which weight of oil to use, the owners manual has clear guidelines on that subject. A single oil viscosity will not be appropriate for all owners. The correct one to use will depend on your climate. I see you are in Missouri. The temperature range there is almost identical to what we have here in Northeastern Oklahoma.

So a 0w-40 will be the recommended weight** to use for year round temeratures. Some of the other recommended viscosities for us are OK for either summer or for winter temperature extremes, but not OK for both summer and winter. I would advise changing the oil and filter yearly, just before the car is put away for winter storage, if you do that.

Synthetic vs. conventional dino oil ? Without cost being a factor, there is plenty of research available that makes a definitive case for the superiority of a quality synthetic oil. Especially when it comes to reducing engine wear.

Everyone has a favorite brand, one that has worked well for them for many years. So there's a lot of brand loyalty. The one I use is Mobil 1 0w-40. But there are many good choices when picking a brand. I like the Mobil 1 0w-40 because:
a) it's used by many european manufacturers of high performance cars with engines similar in design and performance to our XK's
b) it's available everywhere
c) @ $25 for a 5 quart jug, the cost is reasonable, much less than the pricey boutique oils, and not that much more than a quality conventional oil, if price is a concern.


Z

** according to my 2002 Vehicle Care manual section 3-7, if the lows are in the 50 (F) range and the highs are in the 100's (F) or higher, thenrecommended oils are the 0w-40 on the low end of that range and a 5w-40 for the upper range.

 

If you look through these forums you'll see so much written about this question, and nothing definitive. In short, a wide range of oils will work just fine, so all of the talking is around the edges.

Folks agree easily on 90% of the answer: anywhere between 5w-30, 0w-40, and 5w-40 will be fine. Then they'll spend pages debating the other 10%, talking brands, SN ratings, and even the history of the Mexican automotive scene (not joking there!).

Change your oil often, use good filters, and use widely available SN and/or ACEA rated oil in a common weight like those listed above, and your car will last and run as well as any oil will run it. Sure, super special babying may squeeze a little extra life or fuel efficiency out of the engine, but that gets into a realm of diminishing returns.

 

wanted to add to what Zray said here and something that we discussed in another thread as they are both related in my actual experience. in the other thread, Zray asked about achieving high mileage mostly related to these engines. my experience with these engines is limited, however with other very modern and very classic is extensive. the same logic should apply regarding oil types.

my vehicles of choice for regular use are Honda from the eighties to the present. the actual vehicles are driven in some cases over 800,000 US Miles and performed most of my own maintenance including engine overhauls and major repairs. in addition fate gave me access to one of the company's top mechanics. finally, genuine parts are always used unless something is simply not available or the factory original part has a known defect. all of my vehicles are run on full synthetic oil in the variant approved by the manufacturer since acquisition or new, mostly the latter. one, the previous owner did the same as me, so it is consistent. the synthetic oil of choice is Mobile 1, years later discovered Amsoil when there was some concern over the quality of the new 20 viscosity quality. oil filters were always genuine until Honda changed their supplier to another one that caused some concern. then started purchasing filters through Amsoil. the recommended service intervals are followed understanding the true difference between severe and normal service which most people do not.

given the above, something is discovered. there are items which wear more quickly in engines while others have double or triple the lifespan. this means that an engine "failure" or worn condition is specific to particular parts and does not require a full rebuild or replacement even though these are the usual options considered along with vehicle replacement. what does this have to do with a specialty or collectible automobile.

my experience with synthetic oils controlling for proper maintenance and outright abuse is that major components of the engines last much longer and allow for simpler repairs at very high mileage and operating time usage. at much over 300K miles my early 90s specimen only needed rings and valve seals. on this particular engine it was possible to remove the pistons from the bottom of an installed engine, a rather easy job over a weekend. two crossed over 600K before any of this was necessary. testing by my technician contact proved that the bearing surfaces were fine and that oil pressure was within the RPM range specification. all other rotating components were within spec and most seals did not leak.

the reason that this is important is that full rebuilds to factory specification are expensive to do properly and outside of the ability of someone who needs to send parts out for testing and machine work regardless of skill level. however anyone can learn to hone cylinders and install the next ring size. yes, our engines probably require removal from the car to access the bottom end, however there are massive savings worth the effort. an early car might not even need cylinder honing and these rings might last even longer.

additionally the complete absence of varnish and sludge means that the block does not have to be cleaned with concern to oil passages. it is also nice to work on.

for direct comparison using the data from the thousands of cars serviced through my contact's mechanic shop, the cars that were maintained on schedule properly, not abused using conventional oil or blends required complete engine replacement or rebuild at somewhat less than the mileage where my cars were wearing out the specific items described above. no one really complained that a car needed such overhaul or total vehicle replacement in my market at those 300-400K mileages which are still respectable. none ever reached the 600K that mine did with only basic and scheduled maintenance.

in a collectible car and/or in a frugal situation combining with mechanical ability, the use of synthetic oils allows much longer engine lifespans and makes possible less expensive major maintenance. one can learn how to do these jobs and enjoy the challenge. rebuilding is of course possible to learn even on the most modern engine, but transporting for machine work gets old fast.

another takeaway is that an engine which is getting tired, not abused, run on good oil might not need a full rebuild but rather someone to do what is described above. remember for your mechanic it is simpler for him just to send your engine out with his only work being removal and reinstall. you pay for his convenience.

another question that i am always asked concerns the million mile with little mechanical work. this is probably due to much highway and high speed driving where the engine run time per mile is much lower than mixed driving. most of my vehicles are mixed. Zray has a good chance of achieving this or close to it.

very important is to not make one problem cause another. if oil consumption goes up and it is due to a set of worn rings after eliminating other factors, then it is more sensible to replace the rings or in the interim add oil instead of ruining other parts such as bearings with thickening agents or out of specification oil. then you will need a complete rebuild. note: never once did i ever replace an oil pump. perhaps specific to the car brand, but worth noting. oil pressure also indicates the condition of the bearings as well as the oil pump.

if i can answer any questions, please ask. yes, this is generalizing to this car, but a lot will hold true.

when people are purchasing used cars i always tell them to find out what oil was used, usually one can find out indirectly by asking where the car was serviced.