Happy New Year everyone, I have question regarding which engine oil, I have a 1995 Jaguar sovereign 4 ltr, it has done 157,000 miles, not sure which oil is best for a higher mileage engine, I have owned the car since 2002 an has been looked after, do I go for fully synthetic, par synthetic or mineral oil, any or all help would be much appreciated
Regards Steve
I only use full synthetic, not because it’s strictly necessary (part synthetic will do) but because it’s the best possible choice. SAE 10W40 or 20W50 depending on where you live.
These engines do not require anything exotic. And they’re famously rugged. I’d be inclined, personally, to keep using the same as I’ve been using all along.
Is there something going on that prompts you to make a change? An increase in oil consumption? A drop in compression? An anticipated change in use or driving conditions?
Sometimes a one-step heavier oil will reduce oil consumption…if that’s a problem you’re having.
There are oils out there specifically marketed as “high mileage” oils. I’ve not researched the real or supposed benefits nor researched the veracity of the manufacturers’ claims.
For its age your car has accumulated relatively few miles. If such low use continues I’m not sure you’d realize any tangible, measurable, real-world benefits of a specialty oil. Other than, perhaps, some extra peace of mind. And there’s nothing wrong with that.
FWIW I had an X300/XJR for many years as a daily driver. Bought it at 30k miles and sold it at 171k miles. I used whatever brand oil was on sale that day, changed every 5k miles. When I sold it the engine was still quite healthy.
Cheers
DD
Graham thank you so much for the reply it’s much appreciated
Thank you Doug, regarding any previous problems there isn’t any, never had an issue oil pressure has always been perfect, the reason I asked which oil is because a garage has always done the service, I am going to do it myself this time so wanted to know which oil to buy, I did research on the web and some were for semi synthetic and others fully synthetic, obviously want the best for my engine but don’t want to pay a small fortune, was looking at semi synthetic 10w/40
Thank you Doug, regarding any previous problems there isn’t any, never had an issue oil pressure has always been perfect, the reason I asked which oil is because a garage has always done the service, I am going to do it myself this time so wanted to know which oil to buy, I did research on the web and some were for semi synthetic and others fully synthetic, obviously want the best for my engine but don’t want to pay a small fortune, was looking at semi synthetic 10w/40
Any decent brand of oil, that’s on sale.
As long as it is to manufacturer specifications it’s probably better for any engine to use a cheap oil and change it a little more often 
Hi, I have a 2002 XJ8 with 78000KM. I use full synthetic. Nulon only. Plus I add Nulon friction modifier to the oil. Have used the friction modifier for 30 years in all my cars. Never had an issue. Started using it when I had a Triumph Stag and was paranoid about the timing chains (no better than bicycle chains) wearing out. Do worry about the timing chains on the Jag so I very happy knowing Nulon will help extend the life of the engine.
Hi Nicholas - I don’t know where in the world you live, but I presume your 2002 XJ8 is a X300? I have a XJ8 X350 3.6L normally aspirated and I use Shell Helix Ultra 5W-40 fully synthetic. There are a lot of myths about which oil is best but the bottom line is, so long as the SAE rating is appropriate for the climate and the oil is a “branded” product of one of the major oil manufacturers, you can’t go far wrong. I don’t know “Nulon” and I shy away from brands that I don’t know because many are made from re-claimed or recycled oil. I also use Wynns Super Charge Oil Treatment. Despite the nay-sayers, I have used this for 50 years in all my cars.