Discovered the dreaded Head Gasket Leak when my resevoir was down. Got the oil changed and analyzed right away. Caught it way early and no wear. Previous sample was Pennzoil Platinum 5W40 Thoughts?
Not sure yet. The synthetics used to really make it seep a lot more than usual, but still never had to add between changes. There are a lot of good chices now. My mechanic recommends conventional if I stay with 3K changes. I was having great luck with 10W30 Rotella, but can't find it anymore. I've been using a 10W30 in Winter and 10W40 in Summer. He's going to fill with conventional and wants me to change out at about 2K, so have a while to decide.
That's because they are both British companies. Back in the 60's and 70's everyone use to think if it was European you had to use Castrol.
Yes, the Rotella T5 10w30 would work well in your Range Rover, as would the Shell Rotella T (T6) synthetic 5W-40, and in my opinion both would be better than Castrol 10W-40. If your going to use Castrol, at least use Syntec 5W-40.
The best oils for your all aluminum V8 is a synthetic 5w40. With the way these engines can fail it is best to have that extra protection at extremes that an syn HDEO can offer. I use either Rotella T6 or Mobil 1 Turbo Diesel Truck. I have Mobil 1 0w40 in there now from the winter but am going back to the Mobil 1 Turbo Diesel Truck. These aluminum engines have many many issues as you are finding out.
Also your iron is high for an engine where the only Fe is in the liners and pump and other odds and ends.