Hi, i just bought a 1997 Jaguar XJ6 w/ 93,000 miles on it. It has a 4.0L Straight 6 engine with aluminum block & heads. I do not know what the previous owner used in this car, but it had a Jaguar oil filter on there. Currently I put in 10W-40 Valvoline MaxLife. I will be taking it down to florida in about 3 weeks.
Once the car gets to florida, where the temps will never be below 40*F, which would be the best mineral oil to run in here (HDD 15W-40 oils have had good reviews). This car has an 8.5 Qt. sump capacity and I plan on putting on a Motor Guard too. So i don't think synthetics will help that much especially with the motor guard on there keepin the oil clean.
Once the car gets to florida, where the temps will never be below 40*F, which would be the best mineral oil to run in here (HDD 15W-40 oils have had good reviews). This car has an 8.5 Qt. sump capacity and I plan on putting on a Motor Guard too. So i don't think synthetics will help that much especially with the motor guard on there keepin the oil clean.