I wondered what the best oil to use in a Jaguar X308 4.0 ?. Euro car parts recommended 10-40 synthetic. I am.mot sure if this is the correct oil.

 

5W-30. I use Castrol GTX High Mileage in mine. It's a synthetic blend, and the car seems happy with it. Parts stores pretty much always have a special with 5 qts and a Purolator filter for about 26 bucks, plus the cost of the extra 2 quarts.
Some swear by synthetic, which is also fine. Just know that you need to stay with synthetic once you start using it. No going back to conventional oil.
To be perfectly honest, the weight of the oil is more important than whether it's synthetic or not, and the most important thing is that the oil and filter be changed on a regular schedule.
-Steve-

 

5W-30 I use Pennzoil Platinum High Mileage Full Synthetic.

 

See owner manual recommendation. Personally i like liqui moly 5w40 or 10w40 in summer. And 5w30 or 10w30 in winter liqui moly . I used oil additive last oil change because i have lifters noise ticking . The noise reduced by 70% i would say .

 

whatever reputable brand 0w40 is on sale over there